初始提交: Gitea 项目代码

modules/markup/markdown/ast.go

@@ -0,0 +1,172 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"html/template"
+	"strconv"
+
+	"github.com/yuin/goldmark/ast"
+)
+
+// Details is a block that contains Summary and details
+type Details struct {
+	ast.BaseBlock
+}
+
+// Dump implements Node.Dump .
+func (n *Details) Dump(source []byte, level int) {
+	ast.DumpHelper(n, source, level, nil, nil)
+}
+
+// KindDetails is the NodeKind for Details
+var KindDetails = ast.NewNodeKind("Details")
+
+// Kind implements Node.Kind.
+func (n *Details) Kind() ast.NodeKind {
+	return KindDetails
+}
+
+// NewDetails returns a new Paragraph node.
+func NewDetails() *Details {
+	return &Details{}
+}
+
+// Summary is a block that contains the summary of details block
+type Summary struct {
+	ast.BaseBlock
+}
+
+// Dump implements Node.Dump .
+func (n *Summary) Dump(source []byte, level int) {
+	ast.DumpHelper(n, source, level, nil, nil)
+}
+
+// KindSummary is the NodeKind for Summary
+var KindSummary = ast.NewNodeKind("Summary")
+
+// Kind implements Node.Kind.
+func (n *Summary) Kind() ast.NodeKind {
+	return KindSummary
+}
+
+// NewSummary returns a new Summary node.
+func NewSummary() *Summary {
+	return &Summary{}
+}
+
+// TaskCheckBoxListItem is a block that represents a list item of a markdown block with a checkbox
+type TaskCheckBoxListItem struct {
+	*ast.ListItem
+	IsChecked      bool
+	SourcePosition int
+}
+
+// KindTaskCheckBoxListItem is the NodeKind for TaskCheckBoxListItem
+var KindTaskCheckBoxListItem = ast.NewNodeKind("TaskCheckBoxListItem")
+
+// Dump implements Node.Dump .
+func (n *TaskCheckBoxListItem) Dump(source []byte, level int) {
+	m := map[string]string{}
+	m["IsChecked"] = strconv.FormatBool(n.IsChecked)
+	m["SourcePosition"] = strconv.FormatInt(int64(n.SourcePosition), 10)
+	ast.DumpHelper(n, source, level, m, nil)
+}
+
+// Kind implements Node.Kind.
+func (n *TaskCheckBoxListItem) Kind() ast.NodeKind {
+	return KindTaskCheckBoxListItem
+}
+
+// NewTaskCheckBoxListItem returns a new TaskCheckBoxListItem node.
+func NewTaskCheckBoxListItem(listItem *ast.ListItem) *TaskCheckBoxListItem {
+	return &TaskCheckBoxListItem{
+		ListItem: listItem,
+	}
+}
+
+// Icon is an inline for a Fomantic UI icon
+type Icon struct {
+	ast.BaseInline
+	Name []byte
+}
+
+// ColorPreview is an inline for a color preview
+type ColorPreview struct {
+	ast.BaseInline
+	Color []byte
+}
+
+// Dump implements Node.Dump.
+func (n *ColorPreview) Dump(source []byte, level int) {
+	m := map[string]string{}
+	m["Color"] = string(n.Color)
+	ast.DumpHelper(n, source, level, m, nil)
+}
+
+// KindColorPreview is the NodeKind for ColorPreview
+var KindColorPreview = ast.NewNodeKind("ColorPreview")
+
+// Kind implements Node.Kind.
+func (n *ColorPreview) Kind() ast.NodeKind {
+	return KindColorPreview
+}
+
+// NewColorPreview returns a new Span node.
+func NewColorPreview(color []byte) *ColorPreview {
+	return &ColorPreview{
+		BaseInline: ast.BaseInline{},
+		Color:      color,
+	}
+}
+
+// Attention is an inline for an attention
+type Attention struct {
+	ast.BaseInline
+	AttentionType string
+}
+
+// Dump implements Node.Dump.
+func (n *Attention) Dump(source []byte, level int) {
+	m := map[string]string{}
+	m["AttentionType"] = n.AttentionType
+	ast.DumpHelper(n, source, level, m, nil)
+}
+
+// KindAttention is the NodeKind for Attention
+var KindAttention = ast.NewNodeKind("Attention")
+
+// Kind implements Node.Kind.
+func (n *Attention) Kind() ast.NodeKind {
+	return KindAttention
+}
+
+// NewAttention returns a new Attention node.
+func NewAttention(attentionType string) *Attention {
+	return &Attention{
+		BaseInline:    ast.BaseInline{},
+		AttentionType: attentionType,
+	}
+}
+
+var KindRawHTML = ast.NewNodeKind("RawHTML")
+
+type RawHTML struct {
+	ast.BaseBlock
+	rawHTML template.HTML
+}
+
+func (n *RawHTML) Dump(source []byte, level int) {
+	m := map[string]string{}
+	m["RawHTML"] = string(n.rawHTML)
+	ast.DumpHelper(n, source, level, m, nil)
+}
+
+func (n *RawHTML) Kind() ast.NodeKind {
+	return KindRawHTML
+}
+
+func NewRawHTML(rawHTML template.HTML) *RawHTML {
+	return &RawHTML{rawHTML: rawHTML}
+}

modules/markup/markdown/convertyaml.go

@@ -0,0 +1,98 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"strings"
+
+	"gitea.dev/modules/htmlutil"
+	"gitea.dev/modules/svg"
+
+	"github.com/yuin/goldmark/ast"
+	east "github.com/yuin/goldmark/extension/ast"
+	"go.yaml.in/yaml/v4"
+)
+
+func nodeToTable(meta *yaml.Node) ast.Node {
+	for meta != nil && meta.Kind == yaml.DocumentNode {
+		meta = meta.Content[0]
+	}
+	if meta == nil {
+		return nil
+	}
+	switch meta.Kind {
+	case yaml.MappingNode:
+		return mappingNodeToTable(meta)
+	case yaml.SequenceNode:
+		return sequenceNodeToTable(meta)
+	default:
+		return ast.NewString([]byte(meta.Value))
+	}
+}
+
+func mappingNodeToTable(meta *yaml.Node) ast.Node {
+	table := east.NewTable()
+	alignments := make([]east.Alignment, 0, len(meta.Content)/2)
+	for i := 0; i < len(meta.Content); i += 2 {
+		alignments = append(alignments, east.AlignNone)
+	}
+
+	headerRow := east.NewTableRow(alignments)
+	valueRow := east.NewTableRow(alignments)
+	for i := 0; i < len(meta.Content); i += 2 {
+		cell := east.NewTableCell()
+
+		cell.AppendChild(cell, nodeToTable(meta.Content[i]))
+		headerRow.AppendChild(headerRow, cell)
+
+		if i+1 < len(meta.Content) {
+			cell = east.NewTableCell()
+			cell.AppendChild(cell, nodeToTable(meta.Content[i+1]))
+			valueRow.AppendChild(valueRow, cell)
+		}
+	}
+
+	table.AppendChild(table, east.NewTableHeader(headerRow))
+	table.AppendChild(table, valueRow)
+	return table
+}
+
+func sequenceNodeToTable(meta *yaml.Node) ast.Node {
+	table := east.NewTable()
+	alignments := []east.Alignment{east.AlignNone}
+	for _, item := range meta.Content {
+		row := east.NewTableRow(alignments)
+		cell := east.NewTableCell()
+		cell.AppendChild(cell, nodeToTable(item))
+		row.AppendChild(row, cell)
+		table.AppendChild(table, row)
+	}
+	return table
+}
+
+func nodeToDetails(g *ASTTransformer, meta *yaml.Node) ast.Node {
+	for meta != nil && meta.Kind == yaml.DocumentNode {
+		meta = meta.Content[0]
+	}
+	if meta == nil {
+		return nil
+	}
+	if meta.Kind != yaml.MappingNode {
+		return nil
+	}
+	var keys []string
+	for i := 0; i < len(meta.Content); i += 2 {
+		if meta.Content[i].Kind == yaml.ScalarNode {
+			keys = append(keys, meta.Content[i].Value)
+		}
+	}
+	details := NewDetails()
+	details.SetAttributeString(g.renderInternal.SafeAttr("class"), g.renderInternal.SafeValue("frontmatter-content"))
+	summary := NewSummary()
+	summaryInnerHTML := htmlutil.HTMLFormat("%s %s", svg.RenderHTML("octicon-table", 12), strings.Join(keys, ", "))
+	summary.AppendChild(summary, NewRawHTML(summaryInnerHTML))
+	details.AppendChild(details, summary)
+	details.AppendChild(details, nodeToTable(meta))
+	return details
+}

modules/markup/markdown/goldmark.go

@@ -0,0 +1,218 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"fmt"
+
+	"gitea.dev/modules/container"
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/markup/internal"
+
+	"github.com/yuin/goldmark/ast"
+	east "github.com/yuin/goldmark/extension/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// ASTTransformer is a default transformer of the goldmark tree.
+type ASTTransformer struct {
+	renderInternal *internal.RenderInternal
+	attentionTypes container.Set[string]
+}
+
+func NewASTTransformer(renderInternal *internal.RenderInternal) *ASTTransformer {
+	return &ASTTransformer{
+		renderInternal: renderInternal,
+		attentionTypes: container.SetOf("note", "tip", "important", "warning", "caution"),
+	}
+}
+
+func (g *ASTTransformer) applyElementDir(n ast.Node) {
+	if !markup.RenderBehaviorForTesting.DisableAdditionalAttributes {
+		n.SetAttributeString("dir", "auto")
+	}
+}
+
+// Transform transforms the given AST tree.
+func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc parser.Context) {
+	firstChild := node.FirstChild()
+	ctx := pc.Get(renderContextKey).(*markup.RenderContext)
+	rc := pc.Get(renderConfigKey).(*RenderConfig)
+
+	tocMode := ""
+	if rc.yamlNode != nil {
+		metaNode := rc.toMetaNode(g)
+		if metaNode != nil {
+			node.InsertBefore(node, firstChild, metaNode)
+		}
+		tocMode = rc.TOC
+	}
+
+	_ = ast.Walk(node, func(n ast.Node, entering bool) (ast.WalkStatus, error) {
+		if !entering {
+			return ast.WalkContinue, nil
+		}
+
+		switch v := n.(type) {
+		case *ast.Paragraph:
+			g.applyElementDir(v)
+		case *ast.List:
+			g.transformList(ctx, v, rc)
+		case *ast.Text:
+			if v.SoftLineBreak() && !v.HardLineBreak() {
+				newLineHardBreak := ctx.RenderOptions.Metas["markdownNewLineHardBreak"] == "true"
+				v.SetHardLineBreak(newLineHardBreak)
+			}
+		case *ast.CodeSpan:
+			g.transformCodeSpan(ctx, v, reader)
+		case *ast.FencedCodeBlock:
+			g.transformFencedCodeblock(v, reader)
+		case *ast.Blockquote:
+			return g.transformBlockquote(v, reader)
+		}
+		return ast.WalkContinue, nil
+	})
+
+	if ctx.RenderOptions.EnableHeadingIDGeneration {
+		showTocInMain := tocMode == "true" /* old behavior, in main view */ || tocMode == "main"
+		showTocInSidebar := !showTocInMain && tocMode != "false" // not hidden, not main, then show it in sidebar
+		switch {
+		case showTocInMain:
+			ctx.TocShowInSection = markup.TocShowInMain
+		case showTocInSidebar:
+			ctx.TocShowInSection = markup.TocShowInSidebar
+		}
+	}
+
+	if rc.Lang != "" {
+		node.SetAttributeString("lang", []byte(rc.Lang))
+	}
+}
+
+// NewHTMLRenderer creates a HTMLRenderer to render in the gitea form.
+func NewHTMLRenderer(renderInternal *internal.RenderInternal, opts ...html.Option) renderer.NodeRenderer {
+	r := &HTMLRenderer{
+		renderInternal: renderInternal,
+		Config:         html.NewConfig(),
+	}
+	for _, opt := range opts {
+		opt.SetHTMLOption(&r.Config)
+	}
+	return r
+}
+
+// HTMLRenderer is a renderer.NodeRenderer implementation that
+// renders gitea specific features.
+type HTMLRenderer struct {
+	html.Config
+	renderInternal *internal.RenderInternal
+}
+
+// RegisterFuncs implements renderer.NodeRenderer.RegisterFuncs.
+func (r *HTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(ast.KindDocument, r.renderDocument)
+	reg.Register(KindDetails, r.renderDetails)
+	reg.Register(KindSummary, r.renderSummary)
+	reg.Register(ast.KindCodeSpan, r.renderCodeSpan)
+	reg.Register(ast.KindCodeBlock, r.renderCodeBlock)
+	reg.Register(KindAttention, r.renderAttention)
+	reg.Register(KindTaskCheckBoxListItem, r.renderTaskCheckBoxListItem)
+	reg.Register(east.KindTaskCheckBox, r.renderTaskCheckBox)
+	reg.Register(KindRawHTML, r.renderRawHTML)
+}
+
+// renderCodeBlock wraps indented code blocks like the fenced renderer
+func (r *HTMLRenderer) renderCodeBlock(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		opening := r.renderInternal.ProtectSafeAttrs(`<div class="code-block-container code-overflow-scroll"><pre class="code-block"><code>`)
+		if _, err := w.WriteString(string(opening)); err != nil {
+			return ast.WalkStop, err
+		}
+		lines := n.Lines()
+		for i := 0; i < lines.Len(); i++ {
+			line := lines.At(i)
+			r.Writer.RawWrite(w, line.Value(source))
+		}
+	} else {
+		if _, err := w.WriteString("</code></pre></div>"); err != nil {
+			return ast.WalkStop, err
+		}
+	}
+	return ast.WalkContinue, nil
+}
+
+func (r *HTMLRenderer) renderDocument(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	n := node.(*ast.Document)
+
+	if val, has := n.AttributeString("lang"); has {
+		var err error
+		if entering {
+			_, err = w.WriteString("<div")
+			if err == nil {
+				_, err = fmt.Fprintf(w, ` lang=%q`, val)
+			}
+			if err == nil {
+				_, err = w.WriteRune('>')
+			}
+		} else {
+			_, err = w.WriteString("</div>")
+		}
+
+		if err != nil {
+			return ast.WalkStop, err
+		}
+	}
+
+	return ast.WalkContinue, nil
+}
+
+func (r *HTMLRenderer) renderDetails(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	var err error
+	if entering {
+		if _, err = w.WriteString("<details"); err != nil {
+			return ast.WalkStop, err
+		}
+		html.RenderAttributes(w, node, nil)
+		_, err = w.WriteString(">")
+	} else {
+		_, err = w.WriteString("</details>")
+	}
+
+	if err != nil {
+		return ast.WalkStop, err
+	}
+
+	return ast.WalkContinue, nil
+}
+
+func (r *HTMLRenderer) renderSummary(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	var err error
+	if entering {
+		_, err = w.WriteString("<summary>")
+	} else {
+		_, err = w.WriteString("</summary>")
+	}
+
+	if err != nil {
+		return ast.WalkStop, err
+	}
+
+	return ast.WalkContinue, nil
+}
+
+func (r *HTMLRenderer) renderRawHTML(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	if !entering {
+		return ast.WalkContinue, nil
+	}
+	n := node.(*RawHTML)
+	_, err := w.WriteString(string(r.renderInternal.ProtectSafeAttrs(n.rawHTML)))
+	if err != nil {
+		return ast.WalkStop, err
+	}
+	return ast.WalkContinue, nil
+}

modules/markup/markdown/main_test.go

@@ -0,0 +1,18 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"os"
+	"testing"
+
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/setting"
+)
+
+func TestMain(m *testing.M) {
+	setting.IsInTesting = true
+	markup.RenderBehaviorForTesting.DisableAdditionalAttributes = true
+	os.Exit(m.Run())
+}

modules/markup/markdown/markdown.go

@@ -0,0 +1,303 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"bytes"
+	"errors"
+	"html/template"
+	"io"
+	"strings"
+
+	"gitea.dev/modules/htmlutil"
+	"gitea.dev/modules/log"
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/markup/common"
+	"gitea.dev/modules/markup/markdown/math"
+	"gitea.dev/modules/setting"
+	giteautil "gitea.dev/modules/util"
+
+	chromahtml "github.com/alecthomas/chroma/v2/formatters/html"
+	"github.com/yuin/goldmark"
+	highlighting "github.com/yuin/goldmark-highlighting/v2"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/extension"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+var (
+	renderContextKey = parser.NewContextKey()
+	renderConfigKey  = parser.NewContextKey()
+)
+
+type limitWriter struct {
+	w     io.Writer
+	sum   int64
+	limit int64
+}
+
+// Write implements the standard Write interface:
+func (l *limitWriter) Write(data []byte) (int, error) {
+	leftToWrite := l.limit - l.sum
+	if leftToWrite < int64(len(data)) {
+		n, err := l.w.Write(data[:leftToWrite])
+		l.sum += int64(n)
+		if err != nil {
+			return n, err
+		}
+		return n, errors.New("rendered content too large - truncating render")
+	}
+	n, err := l.w.Write(data)
+	l.sum += int64(n)
+	return n, err
+}
+
+// newParserContext creates a parser.Context with the render context set
+func newParserContext(ctx *markup.RenderContext) parser.Context {
+	pc := parser.NewContext()
+	pc.Set(renderContextKey, ctx)
+	return pc
+}
+
+type GlodmarkRender struct {
+	ctx *markup.RenderContext
+
+	goldmarkMarkdown goldmark.Markdown
+}
+
+func (r *GlodmarkRender) Convert(source []byte, writer io.Writer, opts ...parser.ParseOption) error {
+	return r.goldmarkMarkdown.Convert(source, writer, opts...)
+}
+
+func (r *GlodmarkRender) highlightingRenderer(w util.BufWriter, c highlighting.CodeBlockContext, entering bool) {
+	if entering {
+		languageBytes, _ := c.Language()
+		languageStr := giteautil.IfZero(string(languageBytes), "text")
+
+		preClasses := "code-block"
+		if languageStr == "mermaid" || languageStr == "math" {
+			preClasses += " is-loading"
+		}
+
+		// include language-x class as part of commonmark spec, "chroma" class is used to highlight the code
+		// the "display" class is used by "js/markup/math.ts" to render the code element as a block
+		// the "math.ts" strictly depends on the structure: <pre class="code-block is-loading"><code class="language-math display">...</code></pre>
+		err := r.ctx.RenderInternal.FormatWithSafeAttrs(w, `<div class="code-block-container code-overflow-scroll"><pre class="%s"><code class="chroma language-%s display">`, preClasses, languageStr)
+		if err != nil {
+			return
+		}
+	} else {
+		_, err := w.WriteString("</code></pre></div>")
+		if err != nil {
+			return
+		}
+	}
+}
+
+type goldmarkEmphasisParser struct {
+	parser.InlineParser
+}
+
+func goldmarkNewEmphasisParser() parser.InlineParser {
+	return &goldmarkEmphasisParser{parser.NewEmphasisParser()}
+}
+
+func (s *goldmarkEmphasisParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
+	line, _ := block.PeekLine()
+	if len(line) > 1 && line[0] == '_' {
+		// a special trick to avoid parsing emphasis in filenames like "module/__init__.py"
+		end := bytes.IndexByte(line[1:], '_')
+		mark := bytes.Index(line, []byte("_.py"))
+		// check whether the "end" matches "_.py" or "__.py"
+		if mark != -1 && (end == mark || end == mark-1) {
+			return nil
+		}
+	}
+	return s.InlineParser.Parse(parent, block, pc)
+}
+
+func goldmarkDefaultParser() parser.Parser {
+	return parser.NewParser(parser.WithBlockParsers(parser.DefaultBlockParsers()...),
+		parser.WithInlineParsers([]util.PrioritizedValue{
+			util.Prioritized(parser.NewCodeSpanParser(), 100),
+			util.Prioritized(parser.NewLinkParser(), 200),
+			util.Prioritized(parser.NewAutoLinkParser(), 300),
+			util.Prioritized(parser.NewRawHTMLParser(), 400),
+			util.Prioritized(goldmarkNewEmphasisParser(), 500),
+		}...),
+		parser.WithParagraphTransformers(parser.DefaultParagraphTransformers()...),
+	)
+}
+
+// SpecializedMarkdown sets up the Gitea specific markdown extensions
+func SpecializedMarkdown(ctx *markup.RenderContext) *GlodmarkRender {
+	// TODO: it could use a pool to cache the renderers to reuse them with different contexts
+	// at the moment it is fast enough (see the benchmarks)
+	r := &GlodmarkRender{ctx: ctx}
+	r.goldmarkMarkdown = goldmark.New(
+		goldmark.WithParser(goldmarkDefaultParser()),
+		goldmark.WithExtensions(
+			extension.NewTable(extension.WithTableCellAlignMethod(extension.TableCellAlignAttribute)),
+			extension.Strikethrough,
+			extension.TaskList,
+			extension.DefinitionList,
+			common.FootnoteExtension,
+			highlighting.NewHighlighting(
+				highlighting.WithFormatOptions(
+					chromahtml.WithClasses(true),
+					chromahtml.PreventSurroundingPre(true),
+				),
+				highlighting.WithWrapperRenderer(r.highlightingRenderer),
+			),
+			math.NewExtension(&ctx.RenderInternal, math.Options{
+				Enabled:                  setting.Markdown.EnableMath,
+				ParseInlineDollar:        setting.Markdown.MathCodeBlockOptions.ParseInlineDollar,
+				ParseInlineParentheses:   setting.Markdown.MathCodeBlockOptions.ParseInlineParentheses, // this is a bad syntax "\( ... \)", it conflicts with normal markdown escaping
+				ParseBlockDollar:         setting.Markdown.MathCodeBlockOptions.ParseBlockDollar,
+				ParseBlockSquareBrackets: setting.Markdown.MathCodeBlockOptions.ParseBlockSquareBrackets, //  this is a bad syntax "\[ ... \]", it conflicts with normal markdown escaping
+			}),
+		),
+		goldmark.WithParserOptions(
+			parser.WithAttribute(),
+			parser.WithASTTransformers(util.Prioritized(NewASTTransformer(&ctx.RenderInternal), 10000)),
+		),
+		goldmark.WithRendererOptions(html.WithUnsafe()),
+	)
+
+	// Override the original Tasklist renderer!
+	r.goldmarkMarkdown.Renderer().AddOptions(
+		renderer.WithNodeRenderers(util.Prioritized(NewHTMLRenderer(&ctx.RenderInternal), 10)),
+	)
+
+	return r
+}
+
+// render calls goldmark render to convert Markdown to HTML
+// NOTE: The output of this method MUST get sanitized separately!!!
+func render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
+	converter := SpecializedMarkdown(ctx)
+	lw := &limitWriter{
+		w:     output,
+		limit: setting.UI.MaxDisplayFileSize * 3,
+	}
+
+	// FIXME: Don't read all to memory, but goldmark doesn't support
+	buf, err := io.ReadAll(input)
+	if err != nil {
+		log.Error("Unable to ReadAll: %v", err)
+		return err
+	}
+	buf = giteautil.NormalizeEOL(buf)
+
+	// FIXME: should we include a timeout to abort the renderer if it takes too long?
+	defer func() {
+		err := recover()
+		if err == nil {
+			return
+		}
+
+		log.Error("Panic in markdown: %v\n%s", err, log.Stack(2))
+		escapedHTML := template.HTMLEscapeString(giteautil.UnsafeBytesToString(buf))
+		_, _ = output.Write(giteautil.UnsafeStringToBytes(escapedHTML))
+	}()
+
+	pc := newParserContext(ctx)
+
+	// Preserve original length.
+	bufWithMetadataLength := len(buf)
+
+	rc := &RenderConfig{Meta: markup.RenderMetaAsDetails}
+	buf, _ = ExtractMetadataBytes(buf, rc)
+
+	metaLength := max(bufWithMetadataLength-len(buf), 0)
+	rc.metaLength = metaLength
+
+	pc.Set(renderConfigKey, rc)
+
+	if err := converter.Convert(buf, lw, parser.WithContext(pc)); err != nil {
+		log.Error("Unable to render: %v", err)
+		return err
+	}
+
+	return nil
+}
+
+// MarkupName describes markup's name
+var MarkupName = "markdown"
+
+func init() {
+	markup.RegisterRenderer(Renderer{})
+}
+
+type Renderer struct{}
+
+var _ markup.PostProcessRenderer = (*Renderer)(nil)
+
+func (Renderer) Name() string {
+	return MarkupName
+}
+
+func (Renderer) NeedPostProcess() bool { return true }
+
+func (Renderer) FileNamePatterns() []string {
+	return setting.Markdown.FileNamePatterns
+}
+
+func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
+	return []setting.MarkupSanitizerRule{}
+}
+
+func (Renderer) Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
+	return render(ctx, input, output)
+}
+
+// Render renders Markdown to HTML with all specific handling stuff.
+func Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
+	ctx.RenderOptions.MarkupType = MarkupName
+	return markup.Render(ctx, input, output)
+}
+
+// RenderString renders Markdown string to HTML with all specific handling stuff and return string
+func RenderString(ctx *markup.RenderContext, content string) (template.HTML, error) {
+	var buf strings.Builder
+	if err := Render(ctx, strings.NewReader(content), &buf); err != nil {
+		log.Warn("Unable to RenderString: %v, content: %s", err, giteautil.TruncateRunes(content, 200))
+		err = nil
+		return htmlutil.EscapeString(content), err
+	}
+	return template.HTML(buf.String()), nil
+}
+
+// RenderRaw renders Markdown to HTML without handling special links.
+func RenderRaw(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
+	rd, wr := io.Pipe()
+	defer func() {
+		_ = rd.Close()
+		_ = wr.Close()
+	}()
+
+	go func() {
+		if err := render(ctx, input, wr); err != nil {
+			_ = wr.CloseWithError(err)
+			return
+		}
+		_ = wr.Close()
+	}()
+
+	return markup.SanitizeReader(rd, "", output)
+}
+
+// RenderRawString renders Markdown to HTML without handling special links and return string
+func RenderRawString(ctx *markup.RenderContext, content string) (string, error) {
+	var buf strings.Builder
+	if err := RenderRaw(ctx, strings.NewReader(content), &buf); err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}

modules/markup/markdown/markdown_attention_test.go

@@ -0,0 +1,58 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown_test
+
+import (
+	"strings"
+	"testing"
+
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/markup/markdown"
+	"gitea.dev/modules/svg"
+
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+func TestAttention(t *testing.T) {
+	defer svg.MockIcon("octicon-info")()
+	defer svg.MockIcon("octicon-light-bulb")()
+	defer svg.MockIcon("octicon-report")()
+	defer svg.MockIcon("octicon-alert")()
+	defer svg.MockIcon("octicon-stop")()
+
+	test := func(input, expected string) {
+		result, err := markdown.RenderString(markup.NewTestRenderContext(), input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(result)))
+	}
+	renderAttention := func(attention, icon string) string {
+		tmpl := `<blockquote class="attention-header attention-{attention}"><p><svg class="attention-icon attention-{attention} svg {icon}" width="16" height="16"></svg><strong class="attention-{attention}">{Attention}</strong></p>`
+		tmpl = strings.ReplaceAll(tmpl, "{attention}", attention)
+		tmpl = strings.ReplaceAll(tmpl, "{icon}", icon)
+		tmpl = strings.ReplaceAll(tmpl, "{Attention}", cases.Title(language.English).String(attention))
+		return tmpl
+	}
+
+	test(`
+> [!NOTE]
+> text
+`, renderAttention("note", "octicon-info")+"\n<p>text</p>\n</blockquote>")
+
+	test(`> [!note]`, renderAttention("note", "octicon-info")+"\n</blockquote>")
+	test(`> [!tip]`, renderAttention("tip", "octicon-light-bulb")+"\n</blockquote>")
+	test(`> [!important]`, renderAttention("important", "octicon-report")+"\n</blockquote>")
+	test(`> [!warning]`, renderAttention("warning", "octicon-alert")+"\n</blockquote>")
+	test(`> [!caution]`, renderAttention("caution", "octicon-stop")+"\n</blockquote>")
+
+	// escaped by mdformat
+	test(`> \[!NOTE\]`, renderAttention("note", "octicon-info")+"\n</blockquote>")
+
+	// legacy GitHub style
+	test(`> **warning**`, renderAttention("warning", "octicon-alert")+"\n</blockquote>")
+
+	// edge case (it used to cause panic)
+	test(">\ntext", "<blockquote>\n</blockquote>\n<p>text</p>")
+}

modules/markup/markdown/markdown_benchmark_test.go

@@ -0,0 +1,25 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown_test
+
+import (
+	"testing"
+
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/markup/markdown"
+)
+
+func BenchmarkSpecializedMarkdown(b *testing.B) {
+	// 240856	      4719 ns/op
+	for b.Loop() {
+		markdown.SpecializedMarkdown(&markup.RenderContext{})
+	}
+}
+
+func BenchmarkMarkdownRender(b *testing.B) {
+	// 23202	     50840 ns/op
+	for b.Loop() {
+		_, _ = markdown.RenderString(markup.NewTestRenderContext(), "https://example.com\n- a\n- b\n")
+	}
+}

modules/markup/markdown/markdown_math_test.go

@@ -0,0 +1,318 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"strings"
+	"testing"
+
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/setting"
+	"gitea.dev/modules/test"
+
+	"github.com/stretchr/testify/assert"
+)
+
+const nl = "\n"
+
+func TestMathRender(t *testing.T) {
+	setting.Markdown.MathCodeBlockOptions = setting.MarkdownMathCodeBlockOptions{ParseInlineDollar: true, ParseInlineParentheses: true}
+	testcases := []struct {
+		testcase string
+		expected string
+	}{
+		{
+			"$a$",
+			`<p><code class="language-math">a</code></p>` + nl,
+		},
+		{
+			"$ a $",
+			`<p><code class="language-math">a</code></p>` + nl,
+		},
+		{
+			"$a$$b$",
+			`<p><code class="language-math">a</code><code class="language-math">b</code></p>` + nl,
+		},
+		{
+			"$a$ $b$",
+			`<p><code class="language-math">a</code> <code class="language-math">b</code></p>` + nl,
+		},
+		{
+			`\(a\) \(b\)`,
+			`<p><code class="language-math">a</code> <code class="language-math">b</code></p>` + nl,
+		},
+		{
+			`$a$.`,
+			`<p><code class="language-math">a</code>.</p>` + nl,
+		},
+		{
+			`.$a$`,
+			`<p>.$a$</p>` + nl,
+		},
+		{
+			`$a a$b b$`,
+			`<p>$a a$b b$</p>` + nl,
+		},
+		{
+			`a a$b b`,
+			`<p>a a$b b</p>` + nl,
+		},
+		{
+			`a$b $a a$b b$`,
+			`<p>a$b $a a$b b$</p>` + nl,
+		},
+		{
+			"a$x$", // Pattern: "word$other$" The real world example is: "Price is between US$1 and US$2.", so don't parse this.
+			`<p>a$x$</p>` + nl,
+		},
+		{
+			"$x$a",
+			`<p>$x$a</p>` + nl,
+		},
+		{
+			"$a$ ($b$) [$c$] {$d$}",
+			`<p><code class="language-math">a</code> (<code class="language-math">b</code>) [$c$] {$d$}</p>` + nl,
+		},
+		{
+			"[$a$](link)",
+			`<p><a href="/link" rel="nofollow"><code class="language-math">a</code></a></p>` + nl,
+		},
+		{
+			"$$a$$",
+			`<p><code class="language-math">a</code></p>` + nl,
+		},
+		{
+			"$$a$$ test",
+			`<p><code class="language-math">a</code> test</p>` + nl,
+		},
+		{
+			"test $$a$$",
+			`<p>test <code class="language-math">a</code></p>` + nl,
+		},
+		{
+			`foo $x=\$$ bar`,
+			`<p>foo <code class="language-math">x=\$</code> bar</p>` + nl,
+		},
+		{
+			`$\text{$b$}$`,
+			`<p><code class="language-math">\text{$b$}</code></p>` + nl,
+		},
+		{
+			"a$`b`$c",
+			`<p>a<code class="language-math">b</code>c</p>` + nl,
+		},
+		{
+			"a $`b`$ c",
+			`<p>a <code class="language-math">b</code> c</p>` + nl,
+		},
+		{
+			"a$``b``$c x$```y```$z",
+			`<p>a<code class="language-math">b</code>c x<code class="language-math">y</code>z</p>` + nl,
+		},
+	}
+
+	for _, test := range testcases {
+		t.Run(test.testcase, func(t *testing.T) {
+			res, err := RenderString(markup.NewTestRenderContext(), test.testcase)
+			assert.NoError(t, err)
+			assert.Equal(t, test.expected, string(res))
+		})
+	}
+}
+
+func TestMathRenderBlockIndent(t *testing.T) {
+	setting.Markdown.MathCodeBlockOptions = setting.MarkdownMathCodeBlockOptions{ParseBlockDollar: true, ParseBlockSquareBrackets: true}
+	testcases := []struct {
+		name     string
+		testcase string
+		expected string
+	}{
+		{
+			"indent-0",
+			`
+\[
+\alpha
+\]
+`,
+			`<pre class="code-block is-loading"><code class="language-math display">
+\alpha
+</code></pre>
+`,
+		},
+		{
+			"indent-1",
+			`
+ \[
+ \alpha
+ \]
+`,
+			`<pre class="code-block is-loading"><code class="language-math display">
+\alpha
+</code></pre>
+`,
+		},
+		{
+			"indent-2-mismatch",
+			`
+  \[
+a
+ b
+  c
+   d
+  \]
+`,
+			`<pre class="code-block is-loading"><code class="language-math display">
+a
+b
+c
+ d
+</code></pre>
+`,
+		},
+		{
+			"indent-2",
+			`
+  \[
+  a
+   b
+  c
+  \]
+`,
+			`<pre class="code-block is-loading"><code class="language-math display">
+a
+ b
+c
+</code></pre>
+`,
+		},
+		{
+			"indent-0-oneline",
+			`$$ x $$
+foo`,
+			`<code class="language-math display"> x </code>
+<p>foo</p>
+`,
+		},
+		{
+			"indent-3-oneline",
+			`   $$ x $$<SPACE>
+foo`,
+			`<code class="language-math display"> x </code>
+<p>foo</p>
+`,
+		},
+		{
+			"quote-block",
+			`
+> \[
+> a
+> \]
+> \[
+> b
+> \]
+`,
+			`<blockquote>
+<pre class="code-block is-loading"><code class="language-math display">
+a
+</code></pre>
+<pre class="code-block is-loading"><code class="language-math display">
+b
+</code></pre>
+</blockquote>
+`,
+		},
+		{
+			"list-block",
+			`
+1. a
+   \[
+   x
+   \]
+2. b`,
+			`<ol>
+<li>a
+<pre class="code-block is-loading"><code class="language-math display">
+x
+</code></pre>
+</li>
+<li>b</li>
+</ol>
+`,
+		},
+		{
+			"inline-non-math",
+			`\[x]`,
+			`<p>[x]</p>` + nl,
+		},
+	}
+
+	for _, test := range testcases {
+		t.Run(test.name, func(t *testing.T) {
+			res, err := RenderString(markup.NewTestRenderContext(), strings.ReplaceAll(test.testcase, "<SPACE>", " "))
+			assert.NoError(t, err)
+			assert.Equal(t, test.expected, string(res), "unexpected result for test case:\n%s", test.testcase)
+		})
+	}
+}
+
+func TestMathRenderOptions(t *testing.T) {
+	setting.Markdown.MathCodeBlockOptions = setting.MarkdownMathCodeBlockOptions{}
+	defer test.MockVariableValue(&setting.Markdown.MathCodeBlockOptions)
+	test := func(t *testing.T, expected, input string) {
+		res, err := RenderString(markup.NewTestRenderContext(), input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(res)), "input: %s", input)
+	}
+
+	// default (non-conflict) inline syntax
+	test(t, `<p><code class="language-math">a</code></p>`, "$`a`$")
+
+	// ParseInlineDollar
+	test(t, `<p>$a$</p>`, `$a$`)
+	setting.Markdown.MathCodeBlockOptions.ParseInlineDollar = true
+	test(t, `<p><code class="language-math">a</code></p>`, `$a$`)
+
+	// ParseInlineParentheses
+	test(t, `<p>(a)</p>`, `\(a\)`)
+	setting.Markdown.MathCodeBlockOptions.ParseInlineParentheses = true
+	test(t, `<p><code class="language-math">a</code></p>`, `\(a\)`)
+
+	// ParseBlockDollar
+	test(t, `<p>$$
+a
+$$</p>
+`, `
+$$
+a
+$$
+`)
+	setting.Markdown.MathCodeBlockOptions.ParseBlockDollar = true
+	test(t, `<pre class="code-block is-loading"><code class="language-math display">
+a
+</code></pre>
+`, `
+$$
+a
+$$
+`)
+
+	// ParseBlockSquareBrackets
+	test(t, `<p>[
+a
+]</p>
+`, `
+\[
+a
+\]
+`)
+	setting.Markdown.MathCodeBlockOptions.ParseBlockSquareBrackets = true
+	test(t, `<pre class="code-block is-loading"><code class="language-math display">
+a
+</code></pre>
+`, `
+\[
+a
+\]
+`)
+}

modules/markup/markdown/markdown_test.go

@@ -0,0 +1,623 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown_test
+
+import (
+	"context"
+	"html/template"
+	"strings"
+	"testing"
+
+	"gitea.dev/modules/log"
+	"gitea.dev/modules/markup"
+	"gitea.dev/modules/markup/markdown"
+	"gitea.dev/modules/setting"
+	"gitea.dev/modules/test"
+
+	"github.com/stretchr/testify/assert"
+)
+
+const (
+	AppURL            = "http://localhost:3000/"
+	testRepoOwnerName = "user13"
+	testRepoName      = "repo11"
+)
+
+// these values should match the const above
+var localMetas = map[string]string{
+	"user": testRepoOwnerName,
+	"repo": testRepoName,
+}
+
+func TestRender_StandardLinks(t *testing.T) {
+	test := func(input, expected string) {
+		buffer, err := markdown.RenderString(markup.NewTestRenderContext(), input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(buffer)))
+	}
+
+	googleRendered := `<p><a href="https://google.com/" rel="nofollow">https://google.com/</a></p>`
+	test("<https://google.com/>", googleRendered)
+	test("[Link](Link)", `<p><a href="/Link" rel="nofollow">Link</a></p>`)
+}
+
+func TestRender_Images(t *testing.T) {
+	setting.AppURL = AppURL
+
+	const baseLink = "http://localhost:3000/user13/repo11"
+	render := func(input, expected string) {
+		buffer, err := markdown.RenderString(markup.NewTestRenderContext(baseLink), input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(buffer)))
+	}
+
+	url := "../../.images/src/02/train.jpg"
+	title := "Train"
+	href := "https://gitea.io"
+	result := baseLink + "/.images/src/02/train.jpg" // resolved link should not go out of the base link
+	// hint: With Markdown v2.5.2, there is a new syntax: [link](URL){:target="_blank"} , but we do not support it now
+
+	render(
+		"!["+title+"]("+url+")",
+		`<p><a href="`+result+`" target="_blank" rel="nofollow noopener"><img src="`+result+`" alt="`+title+`"/></a></p>`)
+
+	render(
+		"[["+title+"|"+url+"]]",
+		`<p><a href="`+result+`" rel="nofollow"><img src="`+result+`" title="`+title+`" alt="`+title+`"/></a></p>`)
+	render(
+		"[!["+title+"]("+url+")]("+href+")",
+		`<p><a href="`+href+`" rel="nofollow"><img src="`+result+`" alt="`+title+`"/></a></p>`)
+
+	render(
+		"!["+title+"]("+url+")",
+		`<p><a href="`+result+`" target="_blank" rel="nofollow noopener"><img src="`+result+`" alt="`+title+`"/></a></p>`)
+
+	render(
+		"[["+title+"|"+url+"]]",
+		`<p><a href="`+result+`" rel="nofollow"><img src="`+result+`" title="`+title+`" alt="`+title+`"/></a></p>`)
+	render(
+		"[!["+title+"]("+url+")]("+href+")",
+		`<p><a href="`+href+`" rel="nofollow"><img src="`+result+`" alt="`+title+`"/></a></p>`)
+
+	defer test.MockVariableValue(&markup.RenderBehaviorForTesting.DisableAdditionalAttributes, false)()
+	render(
+		"<a><img src='a.jpg'></a>", // by the way, empty "a" tag will be removed
+		`<p dir="auto"><img src="http://localhost:3000/user13/repo11/a.jpg" loading="lazy"/></p>`)
+}
+
+func TestTotal_RenderString(t *testing.T) {
+	const FullURL = AppURL + testRepoOwnerName + "/" + testRepoName + "/"
+	setting.AppURL = AppURL
+	defer test.MockVariableValue(&markup.RenderBehaviorForTesting.DisableAdditionalAttributes, true)()
+
+	// Test cases without ambiguous links (It is not right to copy a whole file here, instead it should clearly test what is being tested)
+	sameCases := []string{
+		// dear imgui wiki markdown extract: special wiki syntax
+		`Wiki! Enjoy :)
+- [[Links, Language bindings, Engine bindings|Links]]
+- [[Tips]]
+
+See commit 65f1bf27bc
+
+Ideas and codes
+
+- Bezier widget (by @r-lyeh) ` + AppURL + `ocornut/imgui/issues/786
+- Bezier widget (by @r-lyeh) ` + FullURL + `issues/786
+- Node graph editors https://github.com/ocornut/imgui/issues/306
+- [[Memory Editor|memory_editor_example]]
+- [[Plot var helper|plot_var_example]]`,
+		// wine-staging wiki home extract: tables, special wiki syntax, images
+		`## What is Wine Staging?
+**Wine Staging** on website [wine-staging.com](http://wine-staging.com).
+
+## Quick Links
+Here are some links to the most important topics. You can find the full list of pages at the sidebar.
+
+| [[images/icon-install.png]]    | [[Installation]]                                         |
+|--------------------------------|----------------------------------------------------------|
+| [[images/icon-usage.png]]      | [[Usage]]                                                |
+`,
+		// libgdx wiki page: inline images with special syntax
+		`[Excelsior JET](http://www.excelsiorjet.com/) allows you to create native executables for Windows, Linux and Mac OS X.
+
+1. [Package your libGDX application](https://github.com/libgdx/libgdx/wiki/Gradle-on-the-Commandline#packaging-for-the-desktop)
+[[images/1.png]]
+2. Perform a test run by hitting the Run! button.
+[[images/2.png]]
+
+## More tests {#custom-id}
+
+(from https://www.markdownguide.org/extended-syntax/)
+
+### Checkboxes
+
+- [ ] unchecked
+- [x] checked
+- [ ] still unchecked
+
+### Definition list
+
+First Term
+: This is the definition of the first term.
+
+Second Term
+: This is one definition of the second term.
+: This is another definition of the second term.
+
+### Footnotes
+
+Here is a simple footnote,[^1] and here is a longer one.[^bignote]
+
+[^1]: This is the first footnote.
+
+[^bignote]: Here is one with multiple paragraphs and code.
+
+    Indent paragraphs to include them in the footnote.
+
+    ` + "`{ my code }`" + `
+
+    Add as many paragraphs as you like.
+`,
+		`
+- [ ] <!-- rebase-check --> If you want to rebase/retry this PR, click this checkbox.
+
+---
+
+This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
+
+<!-- test-comment -->`,
+	}
+
+	baseURL := ""
+	testAnswers := []string{
+		`<p>Wiki! Enjoy :)</p>
+<ul>
+<li><a href="` + baseURL + `/Links" rel="nofollow">Links, Language bindings, Engine bindings</a></li>
+<li><a href="` + baseURL + `/Tips" rel="nofollow">Tips</a></li>
+</ul>
+<p>See commit <a href="/` + testRepoOwnerName + `/` + testRepoName + `/commit/65f1bf27bc" rel="nofollow"><code>65f1bf27bc</code></a></p>
+<p>Ideas and codes</p>
+<ul>
+<li>Bezier widget (by <a href="/r-lyeh" rel="nofollow">@r-lyeh</a>) <a href="http://localhost:3000/ocornut/imgui/issues/786" class="ref-issue" rel="nofollow">ocornut/imgui#786</a></li>
+<li>Bezier widget (by <a href="/r-lyeh" rel="nofollow">@r-lyeh</a>) <a href="` + FullURL + `issues/786" class="ref-issue" rel="nofollow">#786</a></li>
+<li>Node graph editors <a href="https://github.com/ocornut/imgui/issues/306" rel="nofollow">https://github.com/ocornut/imgui/issues/306</a></li>
+<li><a href="` + baseURL + `/memory_editor_example" rel="nofollow">Memory Editor</a></li>
+<li><a href="` + baseURL + `/plot_var_example" rel="nofollow">Plot var helper</a></li>
+</ul>
+`,
+		`<h2 id="user-content-what-is-wine-staging">What is Wine Staging?</h2>
+<p><strong>Wine Staging</strong> on website <a href="http://wine-staging.com" rel="nofollow">wine-staging.com</a>.</p>
+<h2 id="user-content-quick-links">Quick Links</h2>
+<p>Here are some links to the most important topics. You can find the full list of pages at the sidebar.</p>
+<table>
+<thead>
+<tr>
+<th><a href="` + baseURL + `/images/icon-install.png" rel="nofollow"><img src="` + baseURL + `/images/icon-install.png" title="icon-install.png" alt="images/icon-install.png"/></a></th>
+<th><a href="` + baseURL + `/Installation" rel="nofollow">Installation</a></th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td><a href="` + baseURL + `/images/icon-usage.png" rel="nofollow"><img src="` + baseURL + `/images/icon-usage.png" title="icon-usage.png" alt="images/icon-usage.png"/></a></td>
+<td><a href="` + baseURL + `/Usage" rel="nofollow">Usage</a></td>
+</tr>
+</tbody>
+</table>
+`,
+		`<p><a href="http://www.excelsiorjet.com/" rel="nofollow">Excelsior JET</a> allows you to create native executables for Windows, Linux and Mac OS X.</p>
+<ol>
+<li><a href="https://github.com/libgdx/libgdx/wiki/Gradle-on-the-Commandline#packaging-for-the-desktop" rel="nofollow">Package your libGDX application</a>
+<a href="` + baseURL + `/images/1.png" rel="nofollow"><img src="` + baseURL + `/images/1.png" title="1.png" alt="images/1.png"/></a></li>
+<li>Perform a test run by hitting the Run! button.
+<a href="` + baseURL + `/images/2.png" rel="nofollow"><img src="` + baseURL + `/images/2.png" title="2.png" alt="images/2.png"/></a></li>
+</ol>
+<h2 id="user-content-custom-id">More tests</h2>
+<p>(from <a href="https://www.markdownguide.org/extended-syntax/" rel="nofollow">https://www.markdownguide.org/extended-syntax/</a>)</p>
+<h3 id="user-content-checkboxes">Checkboxes</h3>
+<ul>
+<li class="task-list-item"><input type="checkbox" disabled="" data-source-position="434"/>unchecked</li>
+<li class="task-list-item"><input type="checkbox" disabled="" data-source-position="450" checked=""/>checked</li>
+<li class="task-list-item"><input type="checkbox" disabled="" data-source-position="464"/>still unchecked</li>
+</ul>
+<h3 id="user-content-definition-list">Definition list</h3>
+<dl>
+<dt>First Term</dt>
+<dd>This is the definition of the first term.</dd>
+<dt>Second Term</dt>
+<dd>This is one definition of the second term.</dd>
+<dd>This is another definition of the second term.</dd>
+</dl>
+<h3 id="user-content-footnotes">Footnotes</h3>
+<p>Here is a simple footnote,<sup id="fnref:user-content-1"><a href="#fn:user-content-1" rel="nofollow">1 </a></sup> and here is a longer one.<sup id="fnref:user-content-bignote"><a href="#fn:user-content-bignote" rel="nofollow">2 </a></sup></p>
+<div>
+<hr/>
+<ol>
+<li id="fn:user-content-1">
+<p>This is the first footnote. <a href="#fnref:user-content-1" rel="nofollow">↩︎</a></p>
+</li>
+<li id="fn:user-content-bignote">
+<p>Here is one with multiple paragraphs and code.</p>
+<p>Indent paragraphs to include them in the footnote.</p>
+<p><code>{ my code }</code></p>
+<p>Add as many paragraphs as you like. <a href="#fnref:user-content-bignote" rel="nofollow">↩︎</a></p>
+</li>
+</ol>
+</div>
+`,
+		`<ul>
+<li class="task-list-item"><input type="checkbox" disabled="" data-source-position="3"/> If you want to rebase/retry this PR, click this checkbox.</li>
+</ul>
+<hr/>
+<p>This PR has been generated by <a href="https://github.com/renovatebot/renovate" rel="nofollow">Renovate Bot</a>.</p>
+`,
+	}
+
+	markup.Init(&markup.RenderHelperFuncs{
+		IsUsernameMentionable: func(ctx context.Context, username string) bool {
+			return username == "r-lyeh"
+		},
+	})
+	for i := range sameCases {
+		line, err := markdown.RenderString(markup.NewTestRenderContext(localMetas).WithEnableHeadingIDGeneration(true), sameCases[i])
+		assert.NoError(t, err)
+		assert.Equal(t, testAnswers[i], string(line))
+	}
+}
+
+func TestRender_RenderParagraphs(t *testing.T) {
+	test := func(t *testing.T, str string, cnt int) {
+		res, err := markdown.RenderRawString(markup.NewTestRenderContext(), str)
+		assert.NoError(t, err)
+		assert.Equal(t, cnt, strings.Count(res, "<p"), "Rendered result for unix should have %d paragraph(s) but has %d:\n%s\n", cnt, strings.Count(res, "<p"), res)
+
+		mac := strings.ReplaceAll(str, "\n", "\r")
+		res, err = markdown.RenderRawString(markup.NewTestRenderContext(), mac)
+		assert.NoError(t, err)
+		assert.Equal(t, cnt, strings.Count(res, "<p"), "Rendered result for mac should have %d paragraph(s) but has %d:\n%s\n", cnt, strings.Count(res, "<p"), res)
+
+		dos := strings.ReplaceAll(str, "\n", "\r\n")
+		res, err = markdown.RenderRawString(markup.NewTestRenderContext(), dos)
+		assert.NoError(t, err)
+		assert.Equal(t, cnt, strings.Count(res, "<p"), "Rendered result for windows should have %d paragraph(s) but has %d:\n%s\n", cnt, strings.Count(res, "<p"), res)
+	}
+
+	test(t, "\nOne\nTwo\nThree", 1)
+	test(t, "\n\nOne\nTwo\nThree", 1)
+	test(t, "\n\nOne\nTwo\nThree\n\n\n", 1)
+	test(t, "A\n\nB\nC\n", 2)
+	test(t, "A\n\n\nB\nC\n", 2)
+}
+
+func TestMarkdownRenderRaw(t *testing.T) {
+	testcases := [][]byte{
+		{ // clusterfuzz_testcase_minimized_fuzz_markdown_render_raw_6267570554535936
+			0x2a, 0x20, 0x2d, 0x0a, 0x09, 0x20, 0x60, 0x5b, 0x0a, 0x09, 0x20, 0x60,
+			0x5b,
+		},
+		{ // clusterfuzz_testcase_minimized_fuzz_markdown_render_raw_6278827345051648
+			0x2d, 0x20, 0x2d, 0x0d, 0x09, 0x60, 0x0d, 0x09, 0x60,
+		},
+		{ // clusterfuzz_testcase_minimized_fuzz_markdown_render_raw_6016973788020736[] = {
+			0x7b, 0x63, 0x6c, 0x61, 0x73, 0x73, 0x3d, 0x35, 0x7d, 0x0a, 0x3d,
+		},
+	}
+
+	for _, testcase := range testcases {
+		log.Info("Test markdown render error with fuzzy data: %x, the following errors can be recovered", testcase)
+		_, err := markdown.RenderRawString(markup.NewTestRenderContext(), string(testcase))
+		assert.NoError(t, err)
+	}
+}
+
+func TestRenderSiblingImages_Issue12925(t *testing.T) {
+	testcase := `![image1](/image1)
+![image2](/image2)
+`
+	expected := `<p><a href="/image1" target="_blank" rel="nofollow noopener"><img src="/image1" alt="image1"/></a>
+<a href="/image2" target="_blank" rel="nofollow noopener"><img src="/image2" alt="image2"/></a></p>
+`
+	res, err := markdown.RenderString(markup.NewTestRenderContext(), testcase)
+	assert.NoError(t, err)
+	assert.Equal(t, expected, string(res))
+}
+
+func TestRenderEmojiInLinks_Issue12331(t *testing.T) {
+	testcase := `[Link with emoji :moon: in text](https://gitea.io)`
+	expected := `<p><a href="https://gitea.io" rel="nofollow">Link with emoji <span class="emoji" aria-label="waxing gibbous moon">🌔</span> in text</a></p>
+`
+	res, err := markdown.RenderString(markup.NewTestRenderContext(), testcase)
+	assert.NoError(t, err)
+	assert.Equal(t, template.HTML(expected), res)
+}
+
+func TestColorPreview(t *testing.T) {
+	const nl = "\n"
+	positiveTests := []struct {
+		testcase string
+		expected string
+	}{
+		{ // do not render color names
+			"The CSS class `red` is there",
+			"<p>The CSS class <code>red</code> is there</p>\n",
+		},
+		{ // hex
+			"`#FF0000`",
+			`<p><code>#FF0000<span class="color-preview" style="background-color: #FF0000"></span></code></p>` + nl,
+		},
+		{ // rgb
+			"`rgb(16, 32, 64)`",
+			`<p><code>rgb(16, 32, 64)<span class="color-preview" style="background-color: rgb(16, 32, 64)"></span></code></p>` + nl,
+		},
+		{ // short hex
+			"This is the color white `#0a0`",
+			`<p>This is the color white <code>#0a0<span class="color-preview" style="background-color: #0a0"></span></code></p>` + nl,
+		},
+		{ // hsl
+			"HSL stands for hue, saturation, and lightness. An example: `hsl(0, 100%, 50%)`.",
+			`<p>HSL stands for hue, saturation, and lightness. An example: <code>hsl(0, 100%, 50%)<span class="color-preview" style="background-color: hsl(0, 100%, 50%)"></span></code>.</p>` + nl,
+		},
+		{ // uppercase hsl
+			"HSL stands for hue, saturation, and lightness. An example: `HSL(0, 100%, 50%)`.",
+			`<p>HSL stands for hue, saturation, and lightness. An example: <code>HSL(0, 100%, 50%)<span class="color-preview" style="background-color: HSL(0, 100%, 50%)"></span></code>.</p>` + nl,
+		},
+	}
+
+	for _, test := range positiveTests {
+		res, err := markdown.RenderString(markup.NewTestRenderContext(), test.testcase)
+		assert.NoError(t, err, "Unexpected error in testcase: %q", test.testcase)
+		assert.Equal(t, template.HTML(test.expected), res, "Unexpected result in testcase %q", test.testcase)
+	}
+
+	negativeTests := []string{
+		// not a color code
+		"`FF0000`",
+		// inside a code block
+		"```javascript" + nl + `const red = "#FF0000";` + nl + "```",
+		// no backticks
+		"rgb(166, 32, 64)",
+		// typo
+		"`hsI(0, 100%, 50%)`",
+		// looks like a color but not really
+		"`hsl(40, 60, 80)`",
+	}
+
+	for _, test := range negativeTests {
+		res, err := markdown.RenderString(markup.NewTestRenderContext(), test)
+		assert.NoError(t, err, "Unexpected error in testcase: %q", test)
+		assert.NotContains(t, res, `<span class="color-preview" style="background-color: `, "Unexpected result in testcase %q", test)
+	}
+}
+
+func TestMarkdownFrontmatter(t *testing.T) {
+	testcases := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			"MapInFrontmatter",
+			`---
+key1: val1
+key2: val2
+---
+test
+`,
+			`<details class="frontmatter-content"><summary><span>octicon-table(12/)</span> key1, key2</summary><table>
+<thead>
+<tr>
+<th>key1</th>
+<th>key2</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>val1</td>
+<td>val2</td>
+</tr>
+</tbody>
+</table>
+</details><p>test</p>
+`,
+		},
+
+		{
+			"ListInFrontmatter",
+			`---
+- item1
+- item2
+---
+test
+`,
+			`<hr/>
+<ul>
+<li>item1</li>
+<li>item2</li>
+</ul>
+<hr/>
+<p>test</p>
+`,
+		},
+
+		{
+			"StringInFrontmatter",
+			`---
+anything
+---
+test
+`,
+			`<hr/>
+<h2>anything</h2>
+<p>test</p>
+`,
+		},
+
+		{
+			// data-source-position should take into account YAML frontmatter.
+			"ListAfterFrontmatter",
+			`---
+foo: bar
+---
+- [ ] task 1`,
+			`<details class="frontmatter-content"><summary><span>octicon-table(12/)</span> foo</summary><table>
+<thead>
+<tr>
+<th>foo</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>bar</td>
+</tr>
+</tbody>
+</table>
+</details><ul>
+<li class="task-list-item"><input type="checkbox" disabled="" data-source-position="19"/>task 1</li>
+</ul>
+`,
+		},
+		// we have our own frontmatter parser, don't need to use github.com/yuin/goldmark-meta
+		{
+			"InvalidFrontmatter",
+			`---
+foo
+`,
+			`<hr/>
+<p>foo</p>
+`,
+		},
+	}
+
+	for _, tt := range testcases {
+		t.Run(tt.name, func(t *testing.T) {
+			res, err := markdown.RenderString(markup.NewTestRenderContext(), tt.input)
+			assert.NoError(t, err, "Unexpected error in testcase: %q", tt.name)
+			assert.Equal(t, tt.expected, string(res), "Unexpected result in testcase %q", tt.name)
+		})
+	}
+}
+
+func TestRenderLinks(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, AppURL)()
+	defer test.MockVariableValue(&markup.RenderBehaviorForTesting.DisableAdditionalAttributes, true)()
+
+	input := `  space @mention-user${SPACE}${SPACE}
+/just/a/path.bin
+https://example.com/file.bin
+[local link](file.bin)
+[remote link](https://example.com)
+[[local link|file.bin]]
+[[remote link|https://example.com]]
+![local image](image.jpg)
+![local image](path/file)
+![local image](/path/file)
+![remote image](https://example.com/image.jpg)
+[[local image|image.jpg]]
+[[remote link|https://example.com/image.jpg]]
+https://example.com/user/repo/compare/88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb#hash
+com 88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb pare
+https://example.com/user/repo/commit/88fc37a3c0a4dda553bdcfc80c178a58247f42fb
+com 88fc37a3c0a4dda553bdcfc80c178a58247f42fb mit
+:+1:
+mail@domain.com
+@mention-user test
+#123
+  space${SPACE}${SPACE}
+`
+	input = strings.ReplaceAll(input, "${SPACE}", " ") // replace ${SPACE} with " ", to avoid some editor's auto-trimming
+	expected := `<p>space @mention-user<br/>
+/just/a/path.bin
+<a href="https://example.com/file.bin" rel="nofollow">https://example.com/file.bin</a>
+<a href="/file.bin" rel="nofollow">local link</a>
+<a href="https://example.com" rel="nofollow">remote link</a>
+<a href="/file.bin" rel="nofollow">local link</a>
+<a href="https://example.com" rel="nofollow">remote link</a>
+<a href="/image.jpg" target="_blank" rel="nofollow noopener"><img src="/image.jpg" alt="local image"/></a>
+<a href="/path/file" target="_blank" rel="nofollow noopener"><img src="/path/file" alt="local image"/></a>
+<a href="/path/file" target="_blank" rel="nofollow noopener"><img src="/path/file" alt="local image"/></a>
+<a href="https://example.com/image.jpg" target="_blank" rel="nofollow noopener"><img src="https://example.com/image.jpg" alt="remote image"/></a>
+<a href="/image.jpg" rel="nofollow"><img src="/image.jpg" title="local image" alt="local image"/></a>
+<a href="https://example.com/image.jpg" rel="nofollow"><img src="https://example.com/image.jpg" title="remote link" alt="remote link"/></a>
+<a href="https://example.com/user/repo/compare/88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb#hash" rel="nofollow">https://example.com/user/repo/compare/88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb#hash</a>
+com 88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb pare
+<a href="https://example.com/user/repo/commit/88fc37a3c0a4dda553bdcfc80c178a58247f42fb" rel="nofollow">https://example.com/user/repo/commit/88fc37a3c0a4dda553bdcfc80c178a58247f42fb</a>
+com 88fc37a3c0a4dda553bdcfc80c178a58247f42fb mit
+<span class="emoji" aria-label="thumbs up">👍</span>
+<a href="mailto:mail@domain.com" rel="nofollow">mail@domain.com</a>
+@mention-user test
+#123
+space</p>
+`
+	result, err := markdown.RenderString(markup.NewTestRenderContext(localMetas), input)
+	assert.NoError(t, err)
+	assert.Equal(t, expected, string(result))
+
+	t.Run("LocalCommitAndCompare", func(t *testing.T) {
+		input := `http://localhost:3000/user/repo/commit/88fc37a3c0a4dda553bdcfc80c178a58247f42fb
+http://localhost:3000/user/repo/compare/88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb#hash`
+
+		expected := `<p><a href="http://localhost:3000/user/repo/commit/88fc37a3c0a4dda553bdcfc80c178a58247f42fb" rel="nofollow"><code>88fc37a3c0</code></a>
+<a href="http://localhost:3000/user/repo/compare/88fc37a3c0a4dda553bdcfc80c178a58247f42fb...12fc37a3c0a4dda553bdcfc80c178a58247f42fb#hash" rel="nofollow"><code>88fc37a3c0...12fc37a3c0 (hash)</code></a></p>
+`
+		result, err := markdown.RenderString(markup.NewTestRenderContext(localMetas), input)
+		assert.NoError(t, err)
+		assert.Equal(t, expected, string(result))
+	})
+}
+
+func TestMarkdownLink(t *testing.T) {
+	defer test.MockVariableValue(&markup.RenderBehaviorForTesting.DisableAdditionalAttributes, true)()
+	input := `<a href=foo>link1</a>
+<a href='/foo'>link2</a>
+<a href="#foo">link3</a>`
+	result, err := markdown.RenderString(markup.NewTestRenderContext("/base", localMetas), input)
+	assert.NoError(t, err)
+	assert.Equal(t, `<p><a href="/base/foo" rel="nofollow">link1</a>
+<a href="/base/foo" rel="nofollow">link2</a>
+<a href="#user-content-foo" rel="nofollow">link3</a></p>
+`, string(result))
+
+	input = "https://example.com/__init__.py"
+	result, err = markdown.RenderString(markup.NewTestRenderContext("/base", localMetas), input)
+	assert.NoError(t, err)
+	assert.Equal(t, `<p><a href="https://example.com/__init__.py" rel="nofollow">https://example.com/__init__.py</a></p>
+`, string(result))
+}
+
+func TestMarkdownUlDir(t *testing.T) {
+	defer test.MockVariableValue(&markup.RenderBehaviorForTesting.DisableAdditionalAttributes, false)()
+	result, err := markdown.RenderString(markup.NewTestRenderContext(), `
+* a
+  * b
+`)
+	assert.NoError(t, err)
+	assert.Equal(t, `<ul dir="auto">
+<li>a
+<ul>
+<li>b</li>
+</ul>
+</li>
+</ul>
+`, string(result))
+}
+
+func TestMarkdownCodeBlock(t *testing.T) {
+	testRender := func(input, expected string) {
+		buffer, err := markdown.RenderString(markup.NewTestRenderContext(), input)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(string(buffer)))
+	}
+	const nl = "\n"
+	const prefix = `<div class="code-block-container code-overflow-scroll"><pre class="code-block">`
+	const suffix = `</pre></div>`
+
+	testRender("```\ncode\n```", prefix+`<code class="chroma language-text display">code`+nl+`</code>`+suffix)
+
+	const jsCommon = prefix + `<code class="chroma language-js display"><span class="nx">code</span>` + nl + `</code>` + suffix
+	testRender("```js\ncode\n```", jsCommon)
+	testRender("```js:app.ts\ncode\n```", jsCommon)
+	testRender("```js,ignore\ncode\n```", jsCommon)
+	testRender("```js ignore\ncode\n```", jsCommon)
+	testRender("    code\n", prefix+`<code>code`+nl+`</code>`+suffix)
+	testRender("    <script>alert(1)</script>\n", prefix+`<code>&lt;script&gt;alert(1)&lt;/script&gt;`+nl+`</code>`+suffix)
+}

modules/markup/markdown/math/block_node.go

@@ -0,0 +1,42 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import "github.com/yuin/goldmark/ast"
+
+// Block represents a display math block e.g. $$...$$ or \[...\]
+type Block struct {
+	ast.BaseBlock
+	Dollars bool
+	Indent  int
+	Closed  bool
+	Inline  bool
+}
+
+// KindBlock is the node kind for math blocks
+var KindBlock = ast.NewNodeKind("MathBlock")
+
+// NewBlock creates a new math Block
+func NewBlock(dollars bool, indent int) *Block {
+	return &Block{
+		Dollars: dollars,
+		Indent:  indent,
+	}
+}
+
+// Dump dumps the block to a string
+func (n *Block) Dump(source []byte, level int) {
+	m := map[string]string{}
+	ast.DumpHelper(n, source, level, m, nil)
+}
+
+// Kind returns KindBlock for math Blocks
+func (n *Block) Kind() ast.NodeKind {
+	return KindBlock
+}
+
+// IsRaw returns true as this block should not be processed further
+func (n *Block) IsRaw() bool {
+	return true
+}

modules/markup/markdown/math/block_parser.go

@@ -0,0 +1,136 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import (
+	"bytes"
+
+	giteaUtil "gitea.dev/modules/util"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type blockParser struct {
+	parseDollars    bool
+	parseSquare     bool
+	endBytesDollars []byte
+	endBytesSquare  []byte
+}
+
+// NewBlockParser creates a new math BlockParser
+func NewBlockParser(parseDollars, parseSquare bool) parser.BlockParser {
+	return &blockParser{
+		parseDollars:    parseDollars,
+		parseSquare:     parseSquare,
+		endBytesDollars: []byte{'$', '$'},
+		endBytesSquare:  []byte{'\\', ']'},
+	}
+}
+
+// Open parses the current line and returns a result of parsing.
+func (b *blockParser) Open(parent ast.Node, reader text.Reader, pc parser.Context) (ast.Node, parser.State) {
+	line, segment := reader.PeekLine()
+	pos := pc.BlockOffset()
+	if pos == -1 || len(line[pos:]) < 2 {
+		return nil, parser.NoChildren
+	}
+
+	var dollars bool
+	if b.parseDollars && line[pos] == '$' && line[pos+1] == '$' {
+		dollars = true
+	} else if b.parseSquare && line[pos] == '\\' && line[pos+1] == '[' {
+		if len(line[pos:]) >= 3 && line[pos+2] == '!' && bytes.Contains(line[pos:], []byte(`\]`)) {
+			// do not process escaped attention block: "> \[!NOTE\]"
+			return nil, parser.NoChildren
+		}
+		dollars = false
+	} else {
+		return nil, parser.NoChildren
+	}
+
+	node := NewBlock(dollars, pos)
+
+	// Now we need to check if the ending block is on the segment...
+	endBytes := giteaUtil.Iif(dollars, b.endBytesDollars, b.endBytesSquare)
+	idx := bytes.Index(line[pos+2:], endBytes)
+	if idx >= 0 {
+		// for case: "$$ ... $$ any other text" (this case will be handled by the inline parser)
+		for i := pos + 2 + idx + 2; i < len(line); i++ {
+			if line[i] != ' ' && line[i] != '\n' {
+				return nil, parser.NoChildren
+			}
+		}
+		segment.Start += pos + 2
+		segment.Stop = segment.Start + idx
+		node.Lines().Append(segment)
+		node.Closed = true
+		node.Inline = true
+		return node, parser.Close | parser.NoChildren
+	}
+
+	// for case "\[ ... ]" (no close marker on the same line)
+	for i := pos + 2 + idx + 2; i < len(line); i++ {
+		if line[i] != ' ' && line[i] != '\n' {
+			return nil, parser.NoChildren
+		}
+	}
+
+	segment.Start += pos + 2
+	node.Lines().Append(segment)
+	return node, parser.NoChildren
+}
+
+// Continue parses the current line and returns a result of parsing.
+func (b *blockParser) Continue(node ast.Node, reader text.Reader, pc parser.Context) parser.State {
+	block := node.(*Block)
+	if block.Closed {
+		return parser.Close
+	}
+
+	line, segment := reader.PeekLine()
+	w, pos := util.IndentWidth(line, reader.LineOffset())
+	if w < 4 {
+		endBytes := giteaUtil.Iif(block.Dollars, b.endBytesDollars, b.endBytesSquare)
+		if bytes.HasPrefix(line[pos:], endBytes) && util.IsBlank(line[pos+len(endBytes):]) {
+			if util.IsBlank(line[pos+len(endBytes):]) {
+				newline := giteaUtil.Iif(line[len(line)-1] != '\n', 0, 1)
+				reader.Advance(segment.Stop - segment.Start - newline + segment.Padding)
+				return parser.Close
+			}
+		}
+	}
+	start := segment.Start + giteaUtil.Iif(pos > block.Indent, block.Indent, pos)
+	seg := text.NewSegmentPadding(start, segment.Stop, segment.Padding)
+	node.Lines().Append(seg)
+	return parser.Continue | parser.NoChildren
+}
+
+// Close will be called when the parser returns Close.
+func (b *blockParser) Close(node ast.Node, reader text.Reader, pc parser.Context) {
+	// noop
+}
+
+// CanInterruptParagraph returns true if the parser can interrupt paragraphs,
+// otherwise false.
+func (b *blockParser) CanInterruptParagraph() bool {
+	return true
+}
+
+// CanAcceptIndentedLine returns true if the parser can open new node when
+// the given line is being indented more than 3 spaces.
+func (b *blockParser) CanAcceptIndentedLine() bool {
+	return false
+}
+
+// Trigger returns a list of characters that triggers Parse method of
+// this parser.
+// If Trigger returns a nil, Open will be called with any lines.
+//
+// We leave this as nil as our parse method is quick enough
+func (b *blockParser) Trigger() []byte {
+	return nil
+}

modules/markup/markdown/math/block_renderer.go

@@ -0,0 +1,61 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import (
+	"html/template"
+
+	"gitea.dev/modules/markup/internal"
+	giteaUtil "gitea.dev/modules/util"
+
+	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/util"
+)
+
+// Block render output:
+// 	<pre class="code-block is-loading"><code class="language-math display">...</code></pre>
+//
+// Keep in mind that there is another "code block" render in "func (r *GlodmarkRender) highlightingRenderer"
+// "highlightingRenderer" outputs the math block with extra "chroma" class:
+// 	<pre class="code-block is-loading"><code class="chroma language-math display">...</code></pre>
+//
+// Special classes:
+// * "is-loading": show a loading indicator
+// * "display": used by JS to decide to render as a block, otherwise render as inline
+
+// BlockRenderer represents a renderer for math Blocks
+type BlockRenderer struct {
+	renderInternal *internal.RenderInternal
+}
+
+// NewBlockRenderer creates a new renderer for math Blocks
+func NewBlockRenderer(renderInternal *internal.RenderInternal) renderer.NodeRenderer {
+	return &BlockRenderer{renderInternal: renderInternal}
+}
+
+// RegisterFuncs registers the renderer for math Blocks
+func (r *BlockRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(KindBlock, r.renderBlock)
+}
+
+func (r *BlockRenderer) writeLines(w util.BufWriter, source []byte, n gast.Node) {
+	l := n.Lines().Len()
+	for i := range l {
+		line := n.Lines().At(i)
+		_, _ = w.Write(util.EscapeHTML(line.Value(source)))
+	}
+}
+
+func (r *BlockRenderer) renderBlock(w util.BufWriter, source []byte, node gast.Node, entering bool) (gast.WalkStatus, error) {
+	n := node.(*Block)
+	if entering {
+		codeHTML := giteaUtil.Iif[template.HTML](n.Inline, "", `<pre class="code-block is-loading">`) + `<code class="language-math display">`
+		_, _ = w.WriteString(string(r.renderInternal.ProtectSafeAttrs(codeHTML)))
+		r.writeLines(w, source, n)
+	} else {
+		_, _ = w.WriteString(`</code>` + giteaUtil.Iif(n.Inline, "", `</pre>`) + "\n")
+	}
+	return gast.WalkContinue, nil
+}

modules/markup/markdown/math/inline_node.go

@@ -0,0 +1,48 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/util"
+)
+
+// Inline struct represents inline math e.g. $...$ or \(...\)
+type Inline struct {
+	ast.BaseInline
+}
+
+// Inline implements Inline.Inline.
+func (n *Inline) Inline() {}
+
+// IsBlank returns if this inline node is empty
+func (n *Inline) IsBlank(source []byte) bool {
+	for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+		text := c.(*ast.Text).Segment
+		if !util.IsBlank(text.Value(source)) {
+			return false
+		}
+	}
+	return true
+}
+
+// Dump renders this inline math as debug
+func (n *Inline) Dump(source []byte, level int) {
+	ast.DumpHelper(n, source, level, nil, nil)
+}
+
+// KindInline is the kind for math inline
+var KindInline = ast.NewNodeKind("MathInline")
+
+// Kind returns KindInline
+func (n *Inline) Kind() ast.NodeKind {
+	return KindInline
+}
+
+// NewInline creates a new ast math inline node
+func NewInline() *Inline {
+	return &Inline{
+		BaseInline: ast.BaseInline{},
+	}
+}

modules/markup/markdown/math/inline_parser.go

@@ -0,0 +1,175 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import (
+	"bytes"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+)
+
+type inlineParser struct {
+	trigger              []byte
+	endBytesSingleDollar []byte
+	endBytesDoubleDollar []byte
+	endBytesParentheses  []byte
+	enableInlineDollar   bool
+}
+
+func NewInlineDollarParser(enableInlineDollar bool) parser.InlineParser {
+	return &inlineParser{
+		trigger:              []byte{'$'},
+		endBytesSingleDollar: []byte{'$'},
+		endBytesDoubleDollar: []byte{'$', '$'},
+		enableInlineDollar:   enableInlineDollar,
+	}
+}
+
+var defaultInlineParenthesesParser = &inlineParser{
+	trigger:             []byte{'\\', '('},
+	endBytesParentheses: []byte{'\\', ')'},
+}
+
+func NewInlineParenthesesParser() parser.InlineParser {
+	return defaultInlineParenthesesParser
+}
+
+// Trigger triggers this parser on $ or \
+func (parser *inlineParser) Trigger() []byte {
+	return parser.trigger
+}
+
+func isPunctuation(b byte) bool {
+	return b == '.' || b == '!' || b == '?' || b == ',' || b == ';' || b == ':'
+}
+
+func isParenthesesClose(b byte) bool {
+	return b == ')'
+}
+
+func isAlphanumeric(b byte) bool {
+	return (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9')
+}
+
+func isInMarkdownLinkText(block text.Reader, lineAfter []byte) bool {
+	return block.PrecendingCharacter() == '[' && bytes.HasPrefix(lineAfter, []byte("]("))
+}
+
+// Parse parses the current line and returns a result of parsing.
+func (parser *inlineParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
+	line, _ := block.PeekLine()
+
+	if !bytes.HasPrefix(line, parser.trigger) {
+		// We'll catch this one on the next time round
+		return nil
+	}
+
+	var startMarkLen int
+	var stopMark []byte
+	checkSurrounding := true
+	if line[0] == '$' {
+		startMarkLen = 1
+		stopMark = parser.endBytesSingleDollar
+		if len(line) > 1 {
+			switch line[1] {
+			case '$':
+				startMarkLen = 2
+				stopMark = parser.endBytesDoubleDollar
+			case '`':
+				pos := 1
+				for ; pos < len(line) && line[pos] == '`'; pos++ {
+				}
+				startMarkLen = pos
+				stopMark = bytes.Repeat([]byte{'`'}, pos)
+				stopMark[len(stopMark)-1] = '$'
+				checkSurrounding = false
+			}
+		}
+	} else {
+		startMarkLen = 2
+		stopMark = parser.endBytesParentheses
+	}
+
+	if line[0] == '$' && !parser.enableInlineDollar && (len(line) == 1 || line[1] != '`') {
+		return nil
+	}
+
+	if checkSurrounding {
+		precedingCharacter := block.PrecendingCharacter()
+		if precedingCharacter < 256 && (isAlphanumeric(byte(precedingCharacter)) || isPunctuation(byte(precedingCharacter))) {
+			// need to exclude things like `a$` from being considered a start
+			return nil
+		}
+	}
+
+	// move the opener marker point at the start of the text
+	opener := startMarkLen
+
+	// Now look for an ending line
+	depth := 0
+	ender := -1
+	for i := opener; i < len(line); i++ {
+		if depth == 0 && bytes.HasPrefix(line[i:], stopMark) {
+			succeedingCharacter := byte(0)
+			if i+len(stopMark) < len(line) {
+				succeedingCharacter = line[i+len(stopMark)]
+			}
+			// check valid ending character
+			isValidEndingChar := isPunctuation(succeedingCharacter) || isParenthesesClose(succeedingCharacter) ||
+				succeedingCharacter == ' ' || succeedingCharacter == '\n' || succeedingCharacter == 0 ||
+				succeedingCharacter == '$' ||
+				isInMarkdownLinkText(block, line[i+len(stopMark):])
+			if checkSurrounding && !isValidEndingChar {
+				break
+			}
+			ender = i
+			break
+		}
+		if line[i] == '\\' {
+			i++
+			continue
+		}
+		switch line[i] {
+		case '{':
+			depth++
+		case '}':
+			depth--
+		}
+	}
+	if ender == -1 {
+		return nil
+	}
+
+	block.Advance(opener)
+	_, pos := block.Position()
+	node := NewInline()
+
+	segment := pos.WithStop(pos.Start + ender - opener)
+	node.AppendChild(node, ast.NewRawTextSegment(segment))
+	block.Advance(ender - opener + len(stopMark))
+	trimBlock(node, block)
+	return node
+}
+
+func trimBlock(node *Inline, block text.Reader) {
+	if node.IsBlank(block.Source()) {
+		return
+	}
+
+	// trim first space and last space
+	first := node.FirstChild().(*ast.Text)
+	if !(!first.Segment.IsEmpty() && block.Source()[first.Segment.Start] == ' ') {
+		return
+	}
+
+	last := node.LastChild().(*ast.Text)
+	if !(!last.Segment.IsEmpty() && block.Source()[last.Segment.Stop-1] == ' ') {
+		return
+	}
+
+	first.Segment = first.Segment.WithStart(first.Segment.Start + 1)
+	last.Segment = last.Segment.WithStop(last.Segment.Stop - 1)
+}

modules/markup/markdown/math/inline_renderer.go

@@ -0,0 +1,53 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import (
+	"bytes"
+
+	"gitea.dev/modules/markup/internal"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/util"
+)
+
+// Inline render output:
+// <code class="language-math">...</code>
+
+// InlineRenderer is an inline renderer
+type InlineRenderer struct {
+	renderInternal *internal.RenderInternal
+}
+
+// NewInlineRenderer returns a new renderer for inline math
+func NewInlineRenderer(renderInternal *internal.RenderInternal) renderer.NodeRenderer {
+	return &InlineRenderer{renderInternal: renderInternal}
+}
+
+func (r *InlineRenderer) renderInline(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		_, _ = w.WriteString(string(r.renderInternal.ProtectSafeAttrs(`<code class="language-math">`)))
+		for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+			segment := c.(*ast.Text).Segment
+			value := util.EscapeHTML(segment.Value(source))
+			if bytes.HasSuffix(value, []byte("\n")) {
+				_, _ = w.Write(value[:len(value)-1])
+				if c != n.LastChild() {
+					_, _ = w.Write([]byte(" "))
+				}
+			} else {
+				_, _ = w.Write(value)
+			}
+		}
+		return ast.WalkSkipChildren, nil
+	}
+	_, _ = w.WriteString(`</code>`)
+	return ast.WalkContinue, nil
+}
+
+// RegisterFuncs registers the renderer for inline math nodes
+func (r *InlineRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(KindInline, r.renderInline)
+}

modules/markup/markdown/math/math.go

@@ -0,0 +1,60 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package math
+
+import (
+	"gitea.dev/modules/markup/internal"
+	giteaUtil "gitea.dev/modules/util"
+
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/util"
+)
+
+type Options struct {
+	Enabled                  bool
+	ParseInlineDollar        bool // inline $$ xxx $$ text
+	ParseInlineParentheses   bool // inline \( xxx \) text
+	ParseBlockDollar         bool // block $$ multiple-line $$ text
+	ParseBlockSquareBrackets bool // block \[ multiple-line \] text
+}
+
+// Extension is a math extension
+type Extension struct {
+	renderInternal *internal.RenderInternal
+	options        Options
+}
+
+// NewExtension creates a new math extension with the provided options
+func NewExtension(renderInternal *internal.RenderInternal, opts ...Options) *Extension {
+	opt := giteaUtil.OptionalArg(opts)
+	r := &Extension{
+		renderInternal: renderInternal,
+		options:        opt,
+	}
+	return r
+}
+
+// Extend extends goldmark with our parsers and renderers
+func (e *Extension) Extend(m goldmark.Markdown) {
+	if !e.options.Enabled {
+		return
+	}
+
+	var inlines []util.PrioritizedValue
+	if e.options.ParseInlineParentheses {
+		inlines = append(inlines, util.Prioritized(NewInlineParenthesesParser(), 501))
+	}
+	inlines = append(inlines, util.Prioritized(NewInlineDollarParser(e.options.ParseInlineDollar), 502))
+
+	m.Parser().AddOptions(parser.WithInlineParsers(inlines...))
+	m.Parser().AddOptions(parser.WithBlockParsers(
+		util.Prioritized(NewBlockParser(e.options.ParseBlockDollar, e.options.ParseBlockSquareBrackets), 701),
+	))
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(NewBlockRenderer(e.renderInternal), 501),
+		util.Prioritized(NewInlineRenderer(e.renderInternal), 502),
+	))
+}

modules/markup/markdown/meta.go

@@ -0,0 +1,103 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"bytes"
+	"errors"
+	"unicode"
+	"unicode/utf8"
+
+	"go.yaml.in/yaml/v4"
+)
+
+func isYAMLSeparator(line []byte) bool {
+	idx := 0
+	for ; idx < len(line); idx++ {
+		if line[idx] >= utf8.RuneSelf {
+			r, sz := utf8.DecodeRune(line[idx:])
+			if !unicode.IsSpace(r) {
+				return false
+			}
+			idx += sz
+			continue
+		}
+		if line[idx] != ' ' {
+			break
+		}
+	}
+	dashCount := 0
+	for ; idx < len(line); idx++ {
+		if line[idx] != '-' {
+			break
+		}
+		dashCount++
+	}
+	if dashCount < 3 {
+		return false
+	}
+	for ; idx < len(line); idx++ {
+		if line[idx] >= utf8.RuneSelf {
+			r, sz := utf8.DecodeRune(line[idx:])
+			if !unicode.IsSpace(r) {
+				return false
+			}
+			idx += sz
+			continue
+		}
+		if line[idx] != ' ' {
+			return false
+		}
+	}
+	return true
+}
+
+// ExtractMetadata consumes a markdown file, parses YAML frontmatter,
+// and returns the frontmatter metadata separated from the markdown content
+func ExtractMetadata(contents string, out any) (string, error) {
+	body, err := ExtractMetadataBytes([]byte(contents), out)
+	return string(body), err
+}
+
+// ExtractMetadataBytes consumes a Markdown content, parses YAML frontmatter,
+// and returns the frontmatter metadata separated from the Markdown content
+func ExtractMetadataBytes(contents []byte, out any) ([]byte, error) {
+	var front, body []byte
+
+	start, end := 0, len(contents)
+	idx := bytes.IndexByte(contents[start:], '\n')
+	if idx >= 0 {
+		end = start + idx
+	}
+	line := contents[start:end]
+
+	if !isYAMLSeparator(line) {
+		return contents, errors.New("frontmatter must start with a separator line")
+	}
+	frontMatterStart := end + 1
+	for start = frontMatterStart; start < len(contents); start = end + 1 {
+		end = len(contents)
+		idx := bytes.IndexByte(contents[start:], '\n')
+		if idx >= 0 {
+			end = start + idx
+		}
+		line := contents[start:end]
+		if isYAMLSeparator(line) {
+			front = contents[frontMatterStart:start]
+			if end+1 < len(contents) {
+				body = contents[end+1:]
+			}
+			break
+		}
+	}
+
+	if len(front) == 0 {
+		return contents, errors.New("could not determine metadata")
+	}
+
+	if err := yaml.Unmarshal(front, out); err != nil {
+		return contents, err
+	}
+	return body, nil
+}

modules/markup/markdown/meta_test.go

@@ -0,0 +1,107 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// IssueTemplate is a legacy to keep the unit tests working.
+// Copied from structs.IssueTemplate, the original type has been changed a lot to support yaml template.
+type IssueTemplate struct {
+	Name   string   `json:"name" yaml:"name"`
+	Title  string   `json:"title" yaml:"title"`
+	About  string   `json:"about" yaml:"about"`
+	Labels []string `json:"labels" yaml:"labels"`
+	Ref    string   `json:"ref" yaml:"ref"`
+}
+
+func (it *IssueTemplate) Valid() bool {
+	return strings.TrimSpace(it.Name) != "" && strings.TrimSpace(it.About) != ""
+}
+
+func TestExtractMetadata(t *testing.T) {
+	t.Run("ValidFrontAndBody", func(t *testing.T) {
+		var meta IssueTemplate
+		body, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s\n%s", sepTest, frontTest, sepTest, bodyTest), &meta)
+		assert.NoError(t, err)
+		assert.Equal(t, bodyTest, body)
+		assert.Equal(t, metaTest, meta)
+		assert.True(t, meta.Valid())
+	})
+
+	t.Run("NoFirstSeparator", func(t *testing.T) {
+		var meta IssueTemplate
+		_, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s", frontTest, sepTest, bodyTest), &meta)
+		assert.Error(t, err)
+	})
+
+	t.Run("NoLastSeparator", func(t *testing.T) {
+		var meta IssueTemplate
+		_, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s", sepTest, frontTest, bodyTest), &meta)
+		assert.Error(t, err)
+	})
+
+	t.Run("NoBody", func(t *testing.T) {
+		var meta IssueTemplate
+		body, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s", sepTest, frontTest, sepTest), &meta)
+		assert.NoError(t, err)
+		assert.Empty(t, body)
+		assert.Equal(t, metaTest, meta)
+		assert.True(t, meta.Valid())
+	})
+}
+
+func TestExtractMetadataBytes(t *testing.T) {
+	t.Run("ValidFrontAndBody", func(t *testing.T) {
+		var meta IssueTemplate
+		body, err := ExtractMetadataBytes(fmt.Appendf(nil, "%s\n%s\n%s\n%s", sepTest, frontTest, sepTest, bodyTest), &meta)
+		assert.NoError(t, err)
+		assert.Equal(t, bodyTest, string(body))
+		assert.Equal(t, metaTest, meta)
+		assert.True(t, meta.Valid())
+	})
+
+	t.Run("NoFirstSeparator", func(t *testing.T) {
+		var meta IssueTemplate
+		_, err := ExtractMetadataBytes(fmt.Appendf(nil, "%s\n%s\n%s", frontTest, sepTest, bodyTest), &meta)
+		assert.Error(t, err)
+	})
+
+	t.Run("NoLastSeparator", func(t *testing.T) {
+		var meta IssueTemplate
+		_, err := ExtractMetadataBytes(fmt.Appendf(nil, "%s\n%s\n%s", sepTest, frontTest, bodyTest), &meta)
+		assert.Error(t, err)
+	})
+
+	t.Run("NoBody", func(t *testing.T) {
+		var meta IssueTemplate
+		body, err := ExtractMetadataBytes(fmt.Appendf(nil, "%s\n%s\n%s", sepTest, frontTest, sepTest), &meta)
+		assert.NoError(t, err)
+		assert.Empty(t, string(body))
+		assert.Equal(t, metaTest, meta)
+		assert.True(t, meta.Valid())
+	})
+}
+
+var (
+	sepTest   = "-----"
+	frontTest = `name: Test
+about: "A Test"
+title: "Test Title"
+labels:
+  - bug
+  - "test label"`
+	bodyTest = "This is the body"
+	metaTest = IssueTemplate{
+		Name:   "Test",
+		About:  "A Test",
+		Title:  "Test Title",
+		Labels: []string{"bug", "test label"},
+	}
+)

modules/markup/markdown/renderconfig.go

@@ -0,0 +1,121 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"fmt"
+	"strings"
+
+	"gitea.dev/modules/markup"
+
+	"github.com/yuin/goldmark/ast"
+	"go.yaml.in/yaml/v4"
+)
+
+// RenderConfig represents rendering configuration for this file
+type RenderConfig struct {
+	Meta     markup.RenderMetaMode
+	TOC      string // "false": hide,  "side"/empty: in sidebar,  "main"/"true": in main view
+	Lang     string
+	yamlNode *yaml.Node
+
+	// Used internally.  Cannot be controlled by frontmatter.
+	metaLength int
+}
+
+func renderMetaModeFromString(s string) markup.RenderMetaMode {
+	switch strings.TrimSpace(strings.ToLower(s)) {
+	case "none":
+		return markup.RenderMetaAsNone
+	case "table":
+		return markup.RenderMetaAsTable
+	default: // "details"
+		return markup.RenderMetaAsDetails
+	}
+}
+
+// UnmarshalYAML implement yaml.v3 UnmarshalYAML
+func (rc *RenderConfig) UnmarshalYAML(value *yaml.Node) error {
+	if rc == nil {
+		return nil
+	}
+
+	rc.yamlNode = value
+
+	type commonRenderConfig struct {
+		TOC  string `yaml:"include_toc"`
+		Lang string `yaml:"lang"`
+	}
+	var basic commonRenderConfig
+	if err := value.Decode(&basic); err != nil {
+		return fmt.Errorf("unable to decode into commonRenderConfig %w", err)
+	}
+
+	if basic.Lang != "" {
+		rc.Lang = basic.Lang
+	}
+
+	rc.TOC = basic.TOC
+
+	type controlStringRenderConfig struct {
+		Gitea string `yaml:"gitea"`
+	}
+
+	var stringBasic controlStringRenderConfig
+
+	if err := value.Decode(&stringBasic); err == nil {
+		if stringBasic.Gitea != "" {
+			rc.Meta = renderMetaModeFromString(stringBasic.Gitea)
+		}
+		return nil
+	}
+
+	type yamlRenderConfig struct {
+		Meta *string `yaml:"meta"`
+		Icon *string `yaml:"details_icon"` // deprecated, because there is no font icon, so no custom icon
+		TOC  *string `yaml:"include_toc"`
+		Lang *string `yaml:"lang"`
+	}
+
+	type yamlRenderConfigWrapper struct {
+		Gitea *yamlRenderConfig `yaml:"gitea"`
+	}
+
+	var cfg yamlRenderConfigWrapper
+	if err := value.Decode(&cfg); err != nil {
+		return fmt.Errorf("unable to decode into yamlRenderConfigWrapper %w", err)
+	}
+
+	if cfg.Gitea == nil {
+		return nil
+	}
+
+	if cfg.Gitea.Meta != nil {
+		rc.Meta = renderMetaModeFromString(*cfg.Gitea.Meta)
+	}
+
+	if cfg.Gitea.Lang != nil && *cfg.Gitea.Lang != "" {
+		rc.Lang = *cfg.Gitea.Lang
+	}
+
+	if cfg.Gitea.TOC != nil {
+		rc.TOC = *cfg.Gitea.TOC
+	}
+
+	return nil
+}
+
+func (rc *RenderConfig) toMetaNode(g *ASTTransformer) ast.Node {
+	if rc.yamlNode == nil {
+		return nil
+	}
+	switch rc.Meta {
+	case markup.RenderMetaAsTable:
+		return nodeToTable(rc.yamlNode)
+	case markup.RenderMetaAsDetails:
+		return nodeToDetails(g, rc.yamlNode)
+	default:
+		return nil
+	}
+}

modules/markup/markdown/renderconfig_test.go

@@ -0,0 +1,139 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.yaml.in/yaml/v4"
+)
+
+func TestRenderConfig_UnmarshalYAML(t *testing.T) {
+	tests := []struct {
+		name     string
+		expected *RenderConfig
+		args     string
+	}{
+		{
+			"empty", &RenderConfig{
+				Meta: "table",
+				Lang: "",
+			}, "",
+		},
+		{
+			"lang", &RenderConfig{
+				Meta: "table",
+				Lang: "test",
+			}, "lang: test",
+		},
+		{
+			"metatable", &RenderConfig{
+				Meta: "table",
+				Lang: "",
+			}, "gitea: table",
+		},
+		{
+			"metanone", &RenderConfig{
+				Meta: "none",
+				Lang: "",
+			}, "gitea: none",
+		},
+		{
+			"metadetails", &RenderConfig{
+				Meta: "details",
+				Lang: "",
+			}, "gitea: details",
+		},
+		{
+			"metawrong", &RenderConfig{
+				Meta: "details",
+				Lang: "",
+			}, "gitea: wrong",
+		},
+		{
+			"toc", &RenderConfig{
+				TOC:  "true",
+				Meta: "table",
+				Lang: "",
+			}, "include_toc: true",
+		},
+		{
+			"tocfalse", &RenderConfig{
+				TOC:  "false",
+				Meta: "table",
+				Lang: "",
+			}, "include_toc: false",
+		},
+		{
+			"toclang", &RenderConfig{
+				Meta: "table",
+				TOC:  "true",
+				Lang: "testlang",
+			}, `
+				include_toc: true
+				lang: testlang
+				`,
+		},
+		{
+			"complexlang", &RenderConfig{
+				Meta: "table",
+				Lang: "testlang",
+			}, `
+				gitea:
+					lang: testlang
+				`,
+		},
+		{
+			"complexlang2", &RenderConfig{
+				Meta: "table",
+				Lang: "testlang",
+			}, `
+	lang: notright
+	gitea:
+		lang: testlang
+`,
+		},
+		{
+			"complexlang", &RenderConfig{
+				Meta: "table",
+				Lang: "testlang",
+			}, `
+	gitea:
+		lang: testlang
+`,
+		},
+		{
+			"complex2", &RenderConfig{
+				Lang: "two",
+				Meta: "table",
+				TOC:  "true",
+			}, `
+	lang: one
+	include_toc: true
+	gitea:
+		details_icon: smiley
+		meta: table
+		include_toc: true
+		lang: two
+`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := &RenderConfig{
+				Meta: "table",
+				Lang: "",
+			}
+			err := yaml.Unmarshal([]byte(strings.ReplaceAll(tt.args, "\t", "    ")), got)
+			require.NoError(t, err)
+
+			assert.Equal(t, tt.expected.Meta, got.Meta)
+			assert.Equal(t, tt.expected.Lang, got.Lang)
+			assert.Equal(t, tt.expected.TOC, got.TOC)
+		})
+	}
+}

modules/markup/markdown/transform_blockquote.go

@@ -0,0 +1,157 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"strings"
+
+	"gitea.dev/modules/svg"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+// renderAttention renders a quote marked with i.e. "> **Note**" or "> [!Warning]" with a corresponding svg
+func (r *HTMLRenderer) renderAttention(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		n := node.(*Attention)
+		var octiconName string
+		switch n.AttentionType {
+		case "tip":
+			octiconName = "light-bulb"
+		case "important":
+			octiconName = "report"
+		case "warning":
+			octiconName = "alert"
+		case "caution":
+			octiconName = "stop"
+		default: // including "note"
+			octiconName = "info"
+		}
+		svgHTML := svg.RenderHTML("octicon-"+octiconName, 16, "attention-icon attention-"+n.AttentionType)
+		_, _ = w.WriteString(string(r.renderInternal.ProtectSafeAttrs(svgHTML)))
+	}
+	return ast.WalkContinue, nil
+}
+
+func (g *ASTTransformer) extractBlockquoteAttentionEmphasis(firstParagraph ast.Node, reader text.Reader) (string, []ast.Node) {
+	if firstParagraph.ChildCount() < 1 {
+		return "", nil
+	}
+	node1, ok := firstParagraph.FirstChild().(*ast.Emphasis)
+	if !ok {
+		return "", nil
+	}
+	val1 := string(node1.Text(reader.Source())) //nolint:staticcheck // Text is deprecated
+	attentionType := strings.ToLower(val1)
+	if g.attentionTypes.Contains(attentionType) {
+		return attentionType, []ast.Node{node1}
+	}
+	return "", nil
+}
+
+func (g *ASTTransformer) extractBlockquoteAttention2(firstParagraph ast.Node, reader text.Reader) (string, []ast.Node) {
+	if firstParagraph.ChildCount() < 2 {
+		return "", nil
+	}
+	node1, ok := firstParagraph.FirstChild().(*ast.Text)
+	if !ok {
+		return "", nil
+	}
+	node2, ok := node1.NextSibling().(*ast.Text)
+	if !ok {
+		return "", nil
+	}
+	val1 := string(node1.Segment.Value(reader.Source()))
+	val2 := string(node2.Segment.Value(reader.Source()))
+	if strings.HasPrefix(val1, `\[!`) && val2 == `\]` {
+		attentionType := strings.ToLower(val1[3:])
+		if g.attentionTypes.Contains(attentionType) {
+			return attentionType, []ast.Node{node1, node2}
+		}
+	}
+	return "", nil
+}
+
+func (g *ASTTransformer) extractBlockquoteAttention3(firstParagraph ast.Node, reader text.Reader) (string, []ast.Node) {
+	if firstParagraph.ChildCount() < 3 {
+		return "", nil
+	}
+	node1, ok := firstParagraph.FirstChild().(*ast.Text)
+	if !ok {
+		return "", nil
+	}
+	node2, ok := node1.NextSibling().(*ast.Text)
+	if !ok {
+		return "", nil
+	}
+	node3, ok := node2.NextSibling().(*ast.Text)
+	if !ok {
+		return "", nil
+	}
+	val1 := string(node1.Segment.Value(reader.Source()))
+	val2 := string(node2.Segment.Value(reader.Source()))
+	val3 := string(node3.Segment.Value(reader.Source()))
+	if val1 != "[" || val3 != "]" || !strings.HasPrefix(val2, "!") {
+		return "", nil
+	}
+
+	attentionType := strings.ToLower(val2[1:])
+	if g.attentionTypes.Contains(attentionType) {
+		return attentionType, []ast.Node{node1, node2, node3}
+	}
+	return "", nil
+}
+
+func (g *ASTTransformer) transformBlockquote(v *ast.Blockquote, reader text.Reader) (ast.WalkStatus, error) {
+	// We only want attention blockquotes when the AST looks like:
+	// > Text("[") Text("!TYPE") Text("]")
+	// > Text("\[!TYPE") TEXT("\]")
+	// > Text("**TYPE**")
+
+	// grab these nodes and make sure we adhere to the attention blockquote structure
+	firstParagraph := v.FirstChild()
+	if firstParagraph == nil {
+		return ast.WalkContinue, nil
+	}
+	g.applyElementDir(firstParagraph)
+
+	attentionType, processedNodes := g.extractBlockquoteAttentionEmphasis(firstParagraph, reader)
+	if attentionType == "" {
+		attentionType, processedNodes = g.extractBlockquoteAttention2(firstParagraph, reader)
+	}
+	if attentionType == "" {
+		attentionType, processedNodes = g.extractBlockquoteAttention3(firstParagraph, reader)
+	}
+	if attentionType == "" {
+		return ast.WalkContinue, nil
+	}
+
+	// color the blockquote
+	v.SetAttributeString(g.renderInternal.SafeAttr("class"), []byte(g.renderInternal.SafeValue("attention-header attention-"+attentionType)))
+
+	// create an emphasis to make it bold
+	attentionParagraph := ast.NewParagraph()
+	g.applyElementDir(attentionParagraph)
+	emphasis := ast.NewEmphasis(2)
+	emphasis.SetAttributeString(g.renderInternal.SafeAttr("class"), []byte(g.renderInternal.SafeValue("attention-"+attentionType)))
+
+	attentionAstString := ast.NewString([]byte(cases.Title(language.English).String(attentionType)))
+
+	// replace the ![TYPE] with a dedicated paragraph of icon+Type
+	emphasis.AppendChild(emphasis, attentionAstString)
+	attentionParagraph.AppendChild(attentionParagraph, NewAttention(attentionType))
+	attentionParagraph.AppendChild(attentionParagraph, emphasis)
+	firstParagraph.Parent().InsertBefore(firstParagraph.Parent(), firstParagraph, attentionParagraph)
+	for _, processed := range processedNodes {
+		firstParagraph.RemoveChild(firstParagraph, processed)
+	}
+	if firstParagraph.ChildCount() == 0 {
+		firstParagraph.Parent().RemoveChild(firstParagraph.Parent(), firstParagraph)
+	}
+	return ast.WalkContinue, nil
+}

modules/markup/markdown/transform_codeblock.go

@@ -0,0 +1,32 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+)
+
+func (g *ASTTransformer) transformFencedCodeblock(v *ast.FencedCodeBlock, reader text.Reader) {
+	// * Some engines support a meta syntax for appending the filename after the language, separated by a colon
+	//   * https://www.glukhov.org/documentation-tools/markdown/markdown-codeblocks/
+	// * Some engines support additional "options" after the language, separated by a space or comma: ```rust,ignore```
+	//   * https://docs.readme.com/rdmd/docs/code-blocks
+	//   * https://next-book.vercel.app/reference/fencedcode
+	if v.Info == nil {
+		return
+	}
+	info := v.Info.Segment.Value(reader.Source())
+	newEnd := -1
+	for i, b := range info {
+		if b == ' ' || b == ',' || b == ':' {
+			newEnd = i
+			break
+		}
+	}
+	if newEnd != -1 {
+		start := v.Info.Segment.Start
+		v.Info = ast.NewTextSegment(text.NewSegment(start, start+newEnd))
+	}
+}

modules/markup/markdown/transform_codespan.go

@@ -0,0 +1,75 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"bytes"
+	"strings"
+
+	"gitea.dev/modules/markup"
+
+	"github.com/microcosm-cc/bluemonday/css"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// renderCodeSpan renders CodeSpan elements (like goldmark upstream does) but also renders ColorPreview elements.
+// See #21474 for reference
+func (r *HTMLRenderer) renderCodeSpan(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	if entering {
+		if n.Attributes() != nil {
+			_, _ = w.WriteString("<code")
+			html.RenderAttributes(w, n, html.CodeAttributeFilter)
+			_ = w.WriteByte('>')
+		} else {
+			_, _ = w.WriteString("<code>")
+		}
+		for c := n.FirstChild(); c != nil; c = c.NextSibling() {
+			switch v := c.(type) {
+			case *ast.Text:
+				segment := v.Segment
+				value := segment.Value(source)
+				if bytes.HasSuffix(value, []byte("\n")) {
+					r.Writer.RawWrite(w, value[:len(value)-1])
+					r.Writer.RawWrite(w, []byte(" "))
+				} else {
+					r.Writer.RawWrite(w, value)
+				}
+			case *ColorPreview:
+				_ = r.renderInternal.FormatWithSafeAttrs(w, `<span class="color-preview" style="background-color: %s"></span>`, string(v.Color))
+			}
+		}
+		return ast.WalkSkipChildren, nil
+	}
+	_, _ = w.WriteString("</code>")
+	return ast.WalkContinue, nil
+}
+
+// cssColorHandler checks if a string is a render-able CSS color value.
+// The code is from "github.com/microcosm-cc/bluemonday/css.ColorHandler", except that it doesn't handle color words like "red".
+func cssColorHandler(value string) bool {
+	value = strings.ToLower(value)
+	if css.HexRGB.MatchString(value) {
+		return true
+	}
+	if css.RGB.MatchString(value) {
+		return true
+	}
+	if css.RGBA.MatchString(value) {
+		return true
+	}
+	if css.HSL.MatchString(value) {
+		return true
+	}
+	return css.HSLA.MatchString(value)
+}
+
+func (g *ASTTransformer) transformCodeSpan(_ *markup.RenderContext, v *ast.CodeSpan, reader text.Reader) {
+	colorContent := v.Text(reader.Source()) //nolint:staticcheck // Text is deprecated
+	if cssColorHandler(string(colorContent)) {
+		v.AppendChild(v, NewColorPreview(colorContent))
+	}
+}

modules/markup/markdown/transform_list.go

@@ -0,0 +1,96 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"fmt"
+
+	"gitea.dev/modules/markup"
+
+	"github.com/yuin/goldmark/ast"
+	east "github.com/yuin/goldmark/extension/ast"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/util"
+)
+
+func (r *HTMLRenderer) renderTaskCheckBoxListItem(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	n := node.(*TaskCheckBoxListItem)
+	if entering {
+		if n.Attributes() != nil {
+			_, _ = w.WriteString("<li")
+			html.RenderAttributes(w, n, html.ListItemAttributeFilter)
+			_ = w.WriteByte('>')
+		} else {
+			_, _ = w.WriteString("<li>")
+		}
+		fmt.Fprintf(w, `<input type="checkbox" disabled="" data-source-position="%d"`, n.SourcePosition)
+		if n.IsChecked {
+			_, _ = w.WriteString(` checked=""`)
+		}
+		if r.XHTML {
+			_, _ = w.WriteString(` />`)
+		} else {
+			_ = w.WriteByte('>')
+		}
+		fc := n.FirstChild()
+		if fc != nil {
+			if _, ok := fc.(*ast.TextBlock); !ok {
+				_ = w.WriteByte('\n')
+			}
+		}
+	} else {
+		_, _ = w.WriteString("</li>\n")
+	}
+	return ast.WalkContinue, nil
+}
+
+func (r *HTMLRenderer) renderTaskCheckBox(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	return ast.WalkContinue, nil
+}
+
+func (g *ASTTransformer) transformList(_ *markup.RenderContext, v *ast.List, rc *RenderConfig) {
+	if v.HasChildren() {
+		children := make([]ast.Node, 0, v.ChildCount())
+		child := v.FirstChild()
+		for child != nil {
+			children = append(children, child)
+			child = child.NextSibling()
+		}
+		v.RemoveChildren(v)
+
+		for _, child := range children {
+			listItem := child.(*ast.ListItem)
+			if !child.HasChildren() || !child.FirstChild().HasChildren() {
+				v.AppendChild(v, child)
+				continue
+			}
+			taskCheckBox, ok := child.FirstChild().FirstChild().(*east.TaskCheckBox)
+			if !ok {
+				v.AppendChild(v, child)
+				continue
+			}
+			newChild := NewTaskCheckBoxListItem(listItem)
+			newChild.IsChecked = taskCheckBox.IsChecked
+			newChild.SetAttributeString(g.renderInternal.SafeAttr("class"), []byte(g.renderInternal.SafeValue("task-list-item")))
+			segments := newChild.FirstChild().Lines()
+			if segments.Len() > 0 {
+				segment := segments.At(0)
+				newChild.SourcePosition = rc.metaLength + segment.Start
+			}
+			v.AppendChild(v, newChild)
+		}
+	}
+
+	nestedList := false
+	for p := v.Parent(); p != nil; p = p.Parent() {
+		if _, ok := p.(*ast.List); ok {
+			nestedList = true
+			break
+		}
+	}
+	if !nestedList {
+		// "dir=auto" should be only added to top-level "ul". https://github.com/go-gitea/gitea/issues/35058
+		g.applyElementDir(v)
+	}
+}